SMS Guidelines, Regulations & DLT Compliance

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1. Regulatory Framework

Dialing Code +91
Country Name Republic of India (Bharat)
ISO Code IN
Dialing Code +91
Region Asia (South Asia)
Mobile Country Code (MCC) 404 (BSNL, Airtel, Jio, Vi, others) and 405 (Airtel, Jio, Vi, BSNL, Vodafone)
Population (Mobile Subscribers) ~1.18 billion mobile subscribers — world's second-largest mobile market
Time Zone IST — Indian Standard Time (UTC+5:30). No Daylight Saving Time. Entire country is a single time zone.
Two-Way SMS Supported Yes
Number Portability Available Yes — Mobile Number Portability (MNP) fully operational
Concatenated Messages Supported Yes* — with caveats depending on Sender ID type
Message Length (Single SMS) 160 characters (GSM-7) or 70 characters (UCS-2/Unicode)
MMS Support Converted to SMS with embedded URL — no native MMS delivery from international platforms
Sending to Landline Numbers Not possible — API throws error 21614; account not charged
Primary Gateway Options Domestic (DLT-registered, via Indian TSPs) and International (via ILDO connections)
Key Regulatory Body TRAI — Telecom Regulatory Authority of India
Primary Regulation TCCCPR 2018 (Telecom Commercial Communications Customer Preference Regulations), last amended February 12, 2025
Mandatory DLT Registration Yes — for ALL domestic commercial SMS. Required since February 28, 2019.
International Route Available Yes — ILDO route; no DLT required; bypasses DND; different restrictions apply

2. Regulatory Framework

India has one of the world's most structured and technologically sophisticated commercial SMS regulatory ecosystems. At its core is the TCCCPR 2018 — a blockchain-powered framework that governs every commercial message sent to an Indian mobile subscriber. Understanding this multi-layer framework is essential before a single SMS is sent.

2.1 TRAI — Telecom Regulatory Authority of India

The Telecom Regulatory Authority of India (TRAI), established under the TRAI Act 1997, is the apex regulatory authority for telecommunications in India. TRAI issues regulations, directions, and orders governing A2P SMS and commercial communications. Its key instrument for SMS compliance is the Telecom Commercial Communications Customer Preference Regulations (TCCCPR), first enacted in 2018 and significantly amended in February 2025

Reference: TRAI Official Website | TRAI TCCCPR Page

2.2 TCCCPR 2018 — The Core Framework (Amended February 12, 2025)

The Telecom Commercial Communications Customer Preference Regulations (TCCCPR), 2018 were notified on July 19, 2018 and came into full force on February 28, 2019. They superseded the earlier TCCCPR 2010. The TCCCPR 2018 is India's primary legal instrument for regulating commercial SMS and voice communications and is notable globally for being the first telecom regulatory framework in the world to deploy blockchain technology (Distributed Ledger Technology / DLT) for commercial communication governance.

The regulations serve a dual purpose: protecting consumers from Unsolicited Commercial Communications (UCC / spam), while enabling legitimate businesses to communicate with customers who have consented or set appropriate preferences.

Key milestones in TCCCPR evolution:

  1. July 19, 2018: TCCCPR 2018 notified — mandated DLT adoption, Sender/Principal Entity registration, template whitelisting.
  • February 28, 2019: Full enforcement commenced.
  • November 2020: Mandatory DLT registration deadline for all entities sending commercial SMS.
  • February 1, 2021: Template scrubbing fully enforced — unregistered templates blocked at the network level.
  • October 1, 2024: CTA (Call-to-Action) Whitelisting and Variable Tagging mandated — all URLs/links in messages must be pre-approved; all template variables must be pre-tagged.
  • February 12, 2025: Major amendments — new message category suffix system (-P, -S, -T, -G), Service Explicit category discontinued, stricter UCC complaint mechanisms, biometric authentication added to registration, honeypot deployment mandated.
  • May 6, 2025: Header suffix rule effective — all SMS headers automatically carry -P, -S, -T, or -G suffix appended by TSPs during DLT scrubbing.

Reference: TCCCPR 2018 Original Text (TRAI) | TCCCPR 2025 Amendment — Official Gazette

2.3 DLT — The Blockchain Engine Powering India's SMS Ecosystem

Distributed Ledger Technology (DLT) is the blockchain-based platform that underpins all domestic A2P SMS in India. Every entity that sends commercial SMS in India — whether a bank, e-commerce company, hospital, or startup — must be registered on a DLT platform operated by one of the authorised Indian telecom operators. The DLT platform:

  • Records all Principal Entity (PE) registrations and unique Entity IDs
  • Maintains a centralised registry of all approved SMS Headers (Sender IDs)
  • Maintains a registry of all approved Content Templates and Consent Templates
  • Runs real-time scrubbing of every outgoing commercial SMS against DND preferences, approved headers, and approved templates
  • Synchronises data across all operator DLT platforms — so registering once covers all networks
  • Records consumer consent for promotional communications
  • Tracks complaints and enforces blacklisting of violators

As of early 2025, the DLT ecosystem includes approximately 250,000+ registered Principal Entities, 600,000+ registered Headers, and over 55 million approved message templates.

2.4 Digital Personal Data Protection Act, 2023 (DPDP Act)

The Digital Personal Data Protection Act, 2023 (DPDP Act), enacted on August 11, 2023, is India's first comprehensive privacy statute. While its substantive enforcement provisions are still being operationalised (the Data Protection Board of India is yet to be constituted as of early 2026, and the Draft DPDP Rules 2025 are under public consultation), businesses should prepare for full enforcement imminently.

For SMS specifically, the DPDP Act overlays additional consent obligations on top of TCCCPR:

  • Granular Consent: Phone numbers (personal data) may only be used for marketing SMS with specific, informed, freely given, unconditional, and unambiguous consent. Blanket or bundled consent (e.g., a general T&Cs checkbox) is no longer sufficient.
  • Purpose Limitation: Consent obtained for one purpose (e.g., e-commerce delivery alerts) cannot be repurposed for promotional SMS without fresh consent.
  • Right to Withdraw: Subscribers may withdraw consent at any time; withdrawal must be as easy as granting consent.
  • Data Fiduciary Obligations: Businesses processing phone numbers for SMS are 'Data Fiduciaries' with obligations including data minimisation, accuracy, security, and deletion upon purpose completion.
  • Consent Managers: A new institutional category — registered Consent Managers — will manage subscriber consent across platforms.
  • Extraterritorial Scope: The DPDP Act applies to any entity outside India that processes personal data of Indian citizens in connection with offering goods or services in India.
  • Penalties under DPDP Act: Up to ₹50 crore (~USD $6 million) per instance for processing data without valid consent; up to ₹250 crore (~USD $30 million) per incident for data breaches.

Reference: DPDP Act 2023 — Full Text (MeitY) | Draft DPDP Rules 2025

2.5 Other Applicable Legislation

  • Telecom Act, 2023: The new Telecommunications Act (replacing the Telegraph Act, 1885) reinforces powers around subscriber data, interception, and commercial communications.
  • IT Act, 2000 (Sections 43A & 72A): Currently the operative data protection law pending DPDP Act enforcement — imposes liability for breach of sensitive personal data.
  • Consumer Protection Act, 2019 & CCPA Guidelines (2023): Prohibit 'dark patterns' in digital consent collection. Directly relevant to opt-in flows and subscription traps in SMS marketing.
  1. RBI Circular on Digital Payment Security Controls (2021): For banking/fintech entities — mandates specific standards for OTP and transactional SMS delivery.
  • SEBI Circular on Investor Communication: Securities-related SMS must comply with SEBI guidelines in addition to TCCCPR.

Reference: Telecom Act 2023 (DoT) | TRAI TCCCPR Full Resource Page

3. Two Delivery Routes: Domestic vs International

India offers two fundamentally different SMS delivery routes for businesses, each with distinct requirements, capabilities, and trade-offs. Understanding which route is right for your use case is the most important decision before you begin.

Feature Domestic Route International (ILDO) Notes
Who can use it India-registered entities (or via a registered Indian aggregator) Any entity worldwide International companies need DLT only for domestic route
DLT Registration Required YES — mandatory NO This is the defining difference
Sender ID (Header) 6-char alphanumeric brand header (e.g., VM-ABCDEF) — DLT approved. Operator prefix added. Random 5–9 digit ILDO short code (e.g., 54321). No brand ID. DLT route preserves brand identity
DND Bypass Transactional/Service messages bypass DND. Promotional respects DND. Bypasses DND entirely — but only for genuine transactional/opted-in promo International bypasses DND but content still screened
Promotional SMS Supported — with DLT-registered template and DND scrubbing (10 AM–9 PM) Restricted — limited to non-DND numbers in daytime hours without opt-in For promotional at scale, domestic route preferred
OTP / Transactional Supported 24/7 via Service Implicit category Supported 24/7 if truly transactional/OTP Both routes support OTP well
Time Restrictions Promotional: 10 AM–9 PM IST only. Service/Transactional: 24/7. Promotional without consent: 10 AM–9 PM, non-DND only. Opted-in/OTP: 24/7. Same window regardless of route for promo
URL Shorteners Blocked — all URLs must be CTA-whitelisted (since Oct 1, 2024) Generally not allowed — may be filtered No shortened URLs on either route
Delivery Reports (DLR) Reliable for transactional/service. Promotional may vary. Unreliable for promotional (best-effort) Domestic route provides better DLR
Brand Visibility Full brand header visible (e.g., VM-HDFC-T) No brand — random short code shown Domestic wins for brand trust
Best For Recurring communications, OTP, marketing campaigns, full compliance International businesses, one-off OTP, testing Most serious India programmes use domestic
⚠️ Which Route Is Right for You?

If you are an India-registered entity or have a local Indian business entity — use the Domestic Route via DLT registration for full brand visibility, reliable delivery, and promotional capability.

If you are an international company with no Indian entity and primarily need OTP/transactional messages — the International (ILDO) Route can work without DLT registration, but you'll lose brand identity (random short code shown) and promotional capabilities are severely limited.

Not sure which path makes more sense for your business? Our team can assess your use case and recommend the right route from day one — saving you weeks of trial and error.

4. DLT Registration — The Complete Step-by-Step Process

🚨 Critical: No DLT = No Delivery

Since February 2021, telecom operators have been fully enforcing DLT scrubbing. Any SMS submitted to the domestic route from an unregistered entity, with an unregistered header, or matching no approved template will be silently dropped at the network level. The sender receives no error — the message simply never arrives.

4.1  DLT Platforms — Choose One, Covers All

TRAI authorises major Indian telecom operators to host DLT platforms. You only need to register on ONE platform — all DLT platforms are synchronised with each other, so your Entity ID, Headers, and Templates are automatically available across all operators' networks.

DLT Platform URL & Notes
Airtel DLT (Recommended) dltconnect.airtel.in — Strong support, fast approvals. Recommended for most businesses.
Jio TrueConnect trueconnect.jio.com — Popular, good UI. Registration fee: ₹5,900 incl. GST.
Vodafone Idea (VILPOWER) vilpower.in — Vodafone Idea's platform.
BSNL DLT ucc-bsnl.co.in — Government operator; slightly different process.
Tata Teleservices telemarketer.tatateleservices.com — Tata's DLT platform.
Videocon (Ping Connect / SmartPing) smartping.live — Used by some aggregators; recommended for faster approvals by some providers.
MTNL ucc-mtnl.in — Delhi/Mumbai government operator
⭐ We're With You Every Step of the Way

Choosing the right DLT platform matters — some have faster approval queues, better support, and more intuitive interfaces than others. Our team knows exactly which platforms process applications

fastest and where common bottlenecks occur. We can guide you to the right platform and submit your application correctly the first time, avoiding the back-and-forth that delays most first-time registrants by weeks

4.2 Stage 1: Principal Entity (PE) Registration

The Principal Entity (PE) is your company or organisation — the legal entity that authorises commercial SMS to be sent on its behalf. Registering as a PE is the foundation of the entire process. Upon approval, you receive a unique PE ID (Entity ID) that must be passed in the message payload of every SMS you send.

Registration Types:

  • Enterprise (Principal Entity): For any company, institution, or individual that wants to send SMS to its own customers. This is what most businesses register as
  • Telemarketer: For SMS aggregators, resellers, and CPaaS providers that transmit commercial SMS on behalf of other businesses. If you are a CPaaS platform, you register as a Telemarketer (or both).

Documents Required for PE Registration:

  • PAN Card: Business PAN card (mandatory — primary KYC document)
  • GST Certificate: GSTIN (GST Identification Number) certificate
  • Business Registration: Certificate of Incorporation (for companies) / Partnership Deed / Shop & Establishment Certificate / any valid business licence
  • Authorized Signatory PAN & Aadhaar: KYC documents of the person signing on behalf of the entity
  • Letter of Authorization: On company letterhead, authorising the signatory to register on behalf of the company
  • Valid Business Email ID and Mobile Number: Used for OTP verification and communication
  • 2025 Amendment — Biometric Authentication: The February 2025 TCCCPR amendments mandate physical verification and biometric authentication (Aadhaar-based OTP or biometric) for all new registrations. This applies to both PE and Telemarketer registrations

Registration Fee:

  • PE Registration: ₹5,900 (inclusive of GST) — one-time fee. This is the standard fee across Airtel, Jio, Vodafone Idea, and most other operators.
  • BSNL: ₹3,300 (inclusive of GST) — slightly lower
  • Business Registration: Certificate of Incorporation (for companies) / Partnership Deed / Shop & Establishment Certificate / any valid business licence

Approval Timeline:

Entity approval typically takes 24–72 working hours if all documents are correct and complete. Common reasons for delay include mismatches between company name and PAN card, unclear document scans, or missing authorisation letters.

⭐ We're With You Every Step of the Way

PE registration rejections are surprisingly common — documents in regional languages need translation, company names must exactly match the PAN card, and KYC requirements are strictly interpreted. Our team prepares your entire registration package before submission, reviews every document for accuracy, and handles any queries from the operator's verification team. Most of our clients get approved in 24–48 hours.

4.3  Stage 2: Header (Sender ID) Registration

A Header (formerly called Sender ID, now officially termed 'Header' in TRAI regulations) is the unique 6-character alphanumeric identifier that appears as the 'from' name on the recipient's phone. It must represent your brand name or service.

Header Format Rules:

  • Length: Exactly 6 characters for transactional/service headers
  • Case: Uppercase alphabetic (A–Z) only — no numbers in the 6-char header itself (numbers appear in the operator prefix)
  • Brand Relevance: The header must be clearly identifiable as your brand or service. Generic headers (e.g., ALERTS, NOTICE, UPDATE) are rejected
  • Uniqueness: A uniqueness check is enforced — if another entity already has your desired header, you must choose a different one
  • Supporting Document: If the header doesn't obviously correlate with your company name, upload a document proving the relationship (trademark certificate, brand guidelines, etc.)

Header Types (Pre-2025 Amendment Classification):

Header Type Description
Promotional Header 6-digit numeric (e.g., 654789). For marketing/promotional SMS to non-DND numbers. Displayed as a numeric ID to recipients.
Transactional / Service Header (Other) 6-character alphanumeric brand header (e.g., HDFC, SWGGY, AMZN). For OTPs, transaction alerts, service messages. Displayed with operator prefix (e.g., VM-HDFC-T).

May 2025 Update — Header Suffix System:

From May 6, 2025 (per TCCCPR 2025 Amendment), all SMS headers automatically carry a suffix appended by the telecom operator during DLT scrubbing, indicating the message category. Businesses do NOT need to change anything — this is applied automatically by the TSP.

Suffix Category & Description
-T (Transactional) OTPs, bank alerts, transaction confirmations, balance alerts. Triggered within 30 minutes of a customer-initiated transaction. No explicit consent required.
-S (Service) Service Implicit messages — updates to existing customers about products/services they actively use (warranty info, delivery updates, balance alerts, software upgrades). Based on inferred consent from the customer relationship.
-P (Promotional) Marketing and advertising messages. Also now covers former 'Service Explicit' category (post-May 2025). Requires DND compliance and promotional time window. Only sent to subscribers who have not blocked promotional messages or have given explicit consent.
-G (Government) Messages from Central/State Government or TRAI-authorised agencies. Exempt from DND restrictions. Can be sent at any time.
⭐ Service Explicit Category — Discontinued May 7, 2025

The 'Service Explicit' category (which required proof of user consent and allowed service messages with a recommendation component) was discontinued effective May 7, 2025. All existing Service Explicit templates were automatically migrated to the Promotional (-P) category with the same content and header retained. Businesses previously using Service Explicit templates should review whether their messages are now being treated as promotional (subject to DND scrubbing and time window restrictions).

Header Fee:

  • Sender ID/Header Registration: ₹590 per header per year — annual renewal required.
  • Additional headers for the same entity cost the same annual rate.

Header Approval Timeline:

Header approval typically takes 1–3 working days. Unused headers (no traffic for 90 days) are automatically deactivated by operators and must be re-registered.

⭐ We're With You Every Step of the Way

Header selection is deceptively tricky — your chosen 6 characters must be brand-relevant, not already taken, and must pass the operator's approval review. We've seen companies waste days on rejected headers. We advise on the right header choice upfront, check availability before you apply, and prepare the supporting brand documentation to get approval the first time

4.4  Stage 3: Content Template Registration

Every single SMS you intend to send must match a pre-approved Content Template registered on the DLT platform. This is non-negotiable. A message that doesn't match an approved template is silently blocked at the network level. There is no error message; the SMS simply disappears.

Template Categories:

Category Rules & Use Cases
Transactional (-T) Triggered within 30 minutes of a customer-initiated transaction. OTPs, bank alerts, payment confirmations, login codes, refund notifications. No DND restrictions. Can be sent 24/7. Variables like OTP code, amount, date, account number are allowed.
Service Implicit / Service (-S) Communications to existing customers about products/services they currently use, based on inferred consent from the existing relationship. Delivery updates, warranty alerts, software upgrades, balance reminders, appointment confirmations. No explicit consent needed. Can be sent 24/7. Cannot contain promotional content.
Promotional (-P) Marketing messages promoting products or services. Only sent to subscribers who have not blocked promotional communications (DND-compliant) or who have given explicit digital consent. Time-restricted: 10 AM – 9 PM IST only. Promotional content mixed with any other category = treated as Promotional.
Government (-G) Central/State Government or TRAI-authorised communications. Exempt from all DND and time restrictions.

Template Formatting Rules:

  • Brand Name Required: Every template must include your brand name (complete business name, brand name, or trademark) in the content field. This is mandatory.
  • Variables (Placeholders): Dynamic content (OTP codes, names, amounts, order IDs, dates, tracking numbers) is represented by the placeholder {#var#} in templates. A maximum of 5–6 variables is allowed per template. Variables must be pre-tagged by purpose (since October 1, 2024).
  • Variable Tagging (October 1, 2024 Mandate): Each variable must be tagged according to its type — e.g., OTP, amount, account number, date. This prevents misuse of open-ended variables to inject spam content. Variables can only carry the specific data type for which they're tagged.
  • Template ID: Each approved template gets a unique Template ID that must be passed in the message payload alongside the PE ID.
  • Template Ownership: Once approved, the entity retains ownership of that template across all DLT platforms.
  • Template Registration Cost: Free — there is no charge for registering content templates.
  • Template Approval Time: 1–3 working days.

Template Example:

✅ Correct Template Example — OTP

Dear {#var#}, Your OTP for logging into ABCBRAND is {#var#}. Valid for {#var#} minutes. Do not share this with anyone. - ABCBRAND  Variable Tags: [1] Customer name → type: Name | [2] OTP code → type: OTP | [3] Validity → type: Duration Template Category: Transactional (-T) | Header: ABCBRD

🚨 Rejected Template Example

Your {#var#} is {#var#}. {#var#} — ABCBRAND  Reason: Variables not tagged by purpose. Untag open-ended variables are rejected since October 1, 2024.

⭐ We're With You Every Step of the Way

Template registration is where most businesses hit their biggest wall. The October 2024 Variable Tagging requirement alone has caused widespread confusion and registration failures. Our team writes and structures your templates to TRAI specifications, selects the right category (transactional vs service vs promotional), tags all variables correctly, and pre-screens every template before submission. We also maintain your template library and update it whenever your message content changes

4.5 Stage 4: CTA Whitelisting (Mandatory Since October 1, 2024)

Effective October 1, 2024, all Call-to-Action (CTA) elements in SMS templates — including URLs, app download links (APKs), OTT platform links, and any clickable content — must be pre-whitelisted on the DLT platform before they can be included in messages. Any message containing a non-whitelisted URL is automatically scrubbed (blocked) during delivery.

CTA Whitelisting Rules:

  • Mandatory Pre-Approval: Every URL, app link, or OTT link intended for use in SMS must be submitted and approved via the DLT platform before use.
  • No Public URL Shorteners: Shortened URLs (bit.ly, tinyurl, etc.) are blocked. Use full branded URLs or dedicated branded short domains.
  • Domain Ownership Proof: You must demonstrate ownership or authorised use of the URL/domain you wish to whitelist.
  • Scope: Covers all URLs, APK download links, OTT links (WhatsApp, Telegram, etc.) — any clickable or callable element.
  • Existing Templates: All previously approved templates containing URLs must be updated and the URLs whitelisted — retroactively applied.
⭐ We're With You Every Step of the Way

CTA Whitelisting has been one of the biggest sources of delivery failures since October 2024. Many businesses didn't realise their existing templates were being blocked until they noticed delivery drops. We audit your entire template library for CTA compliance, whitelist all your approved domains correctly, and set up a process to whitelist new URLs before your campaigns go live — so you never face a surprise block.

4.6 Stage 5: PE-TM Binding (Linking Your Provider)

The final step before you can send via a Telemarketer (your SMS provider/CPaaS platform) is the PE-TM (Principal Entity – Telemarketer) Binding. This creates a formal, DLT-recorded relationship between your entity and your chosen provider, authorising them to send messages on your behalf.

  • Log in to your DLT account after PE registration is complete.
  • Navigate to 'Telemarketer Request' or equivalent section.
  • Search for your SMS provider/CPaaS by their registered Telemarketer ID (your provider will give you this ID). Add them and submit the binding request.
  • The Telemarketer must accept the binding request from their side.
  • Once bound, your provider can transmit messages using your registered headers and templates.
  • TCCCPR 2025 Restriction: The maximum number of intermediaries between the Principal Entity and the end Telemarketer is now limited (typically one aggregator between PE and final TSP), to ensure full traceability of messages.
⭐ We're With You Every Step of the Way

PE-TM binding sounds simple but it's a step that many businesses forget, causing puzzling delivery failures even after registration is complete. We guide you through the exact binding process for our platform, ensure the binding is confirmed on both sides, and verify end-to-end delivery before you launch.

4.7  DLT Registration Costs Summary

Item Cost
PE Entity Registration ₹5,900 (incl. GST) — one-time, per entity. (BSNL: ₹3,300)
Additional platform registrations Free — synced automatically after first registration
Sender ID / Header Registration ₹590 per header per year — annual renewal required
Content Template Registration Free
CTA URL Whitelisting Free
PE-TM Binding Free
Telemarketer Registration (if applicable) ₹5,900 one-time + ₹590/year per header (renewal after 5 years)
Typical Total for One Entity, One Header ~₹6,490–₹7,000 for first year (one PE + one header)
Additional Headers (each) ₹590/year

4.8  Typical DLT Registration Timeline

Stage Estimated Time
PE Entity Approval 24–72 working hours (1–3 business days)
Header / Sender ID Approval 1–3 working days
Template Approval 1–3 working days
CTA Whitelisting 1–3 working days
PE-TM Binding Same day (both sides accept)
Total Expected Timeline (all steps, no rejections) 5–10 business days
Total with corrections/rejections (common for first-timers) 2–4 weeks
With Expert Assistance 3–7 business days (our team pre-validates everything)

5. Message Categories, DND, and Time Restrictions

5.1  The Four Message Categories (Post-May 2025)

Every commercial SMS in India must be classified into one of four categories. This classification determines: whether the message bypasses DND, when it can be sent, and what consent is required.

Category Description & Rules
Transactional (-T) Customer-initiated, within 30 minutes of a transaction. OTPs, bank alerts, refund info, login codes, payment confirmations. NO DND restrictions. 24/7 delivery. No consent beyond the transaction itself required.
Service Implicit (-S) Service updates to existing customers about products/services they actively use — based on the inferred consent of an existing commercial relationship. Delivery updates, warranty alerts, balance reminders, appointment reminders, software upgrade notices. NO DND restrictions. 24/7 delivery. Cannot contain promotional content — if mixed, treated as Promotional.
Promotional (-P) Advertising and marketing messages. Also covers former Service Explicit (post-May 2025). Subject to DND scrubbing — only delivered to non-DND subscribers or those with explicit digital consent. Time-restricted: 10 AM – 9 PM IST. Must use DLT-registered promotional template.
Government (-G) Central/State Government or TRAI-authorised body communications. Completely exempt from DND and time restrictions. Requires TRAI-approved government header.

5.2  DND — Do Not Disturb Registry

The National Do Not Disturb (DND) Registry (also called the National Customer Preference Register / NCPR) is managed by TRAI and maintained by all telecom operators. Subscribers can register to block all commercial communications or selectively block by category (financial, real estate, education, health, etc.).

DND has several levels:

  • Fully Blocked: All commercial communications blocked, except Transactional, Service Implicit, and Government messages.
  • Partially Blocked: Subscriber allows certain promotional categories. E.g., 'Receive only banking and healthcare promotions.' The DLT scrubbing system checks the promotional category tag in your template against the subscriber's allowed preferences.
  • Not on DND: All commercial communications permitted, subject to time window restrictions for promotional messages.

DLT scrubbing runs in real-time against the DND registry for every outgoing message. Promotional messages to fully blocked numbers are silently dropped. There is no error — the message is simply not delivered.

🎯 Explicit Digital Consent Overrides DND

If a subscriber has given explicit digital consent (via the TRAI-mandated Digital Consent Acquisition / DCA facility) to a specific sender for a specific purpose, promotional messages from that sender CAN be delivered even if the subscriber is on DND. This is a powerful exception — but the consent must be digitally recorded on the DLT Consent Register via the DCA process, which involves OTP verification from the subscriber

5.3 Promotional SMS — Time Restriction

⏰ Promotional SMS: 10:00 AM – 9:00 PM IST Only

All Promotional (-P) SMS messages may only be delivered between 10:00 AM and 9:00 PM Indian Standard Time (IST, UTC+5:30).

India is a single time zone — there is no regional adjustment needed. Messages sent outside this window (9:01 PM – 9:59 AM) are blocked at the DLT scrubbing layer and are NOT queued for later delivery — they are dropped. Transactional (-T) and Service (-S) messages can be sent at any time

5.4  Digital Consent Acquisition (DCA)

The DCA facility, mandated by TRAI (Direction issued June 2, 2023), enables businesses to digitally register customer consent for receiving promotional communications. The process:

  1. Business creates and submits a Consent Template on the DLT platform (distinct from Content Templates).
  1. Customer is presented with the consent request (web, app, IVR, or in-person).
  1. Customer verifies consent via OTP (triggered through the telecom operator).
  1. Consent is recorded on the DLT Consent Register, linked to the subscriber's mobile number.
  1. Business can then send promotional messages to that subscriber regardless of DND status.

Note: Consent via DCA is valid for 12 months from approval date and must be renewed. TRAI acknowledged in 2025 that many businesses find the DCA process restrictive and alternatives are being explored.

6. How SMS Headers Appear to Recipients

Understanding the full structure of an SMS header as it appears on a recipient's phone is important for managing customer expectations and for correctly structuring your Sender ID registration.

Header Type Format & Example
Standard Format (Domestic) XX-HEADER-Y (e.g., VM-HDFC-T) Where: XX = 2-letter operator+circle code | HEADER = your 6-char brand header | -Y = category suffix (-T, -S, -P, or -G, effective May 6, 2025)
Example: Vodafone Mumbai VM-HDFC-T (Vodafone Mumbai, HDFC Bank header, Transactional)
Example: Airtel Delhi AD-AMAZON-S (Airtel Delhi, Amazon header, Service)
Example: Jio Bangalore JB-SWIGGY-P (Jio Bangalore, Swiggy header, Promotional)
International Route Random 5–9 digit numeric code (e.g., 54321 or 56789012) — no brand identity visible
Government Header Exempt from prefix requirements — shown as the registered government header

The two-letter operator+circle code (e.g., VM = Vodafone Mumbai, JB = Jio Bangalore, AD = Airtel Delhi) is automatically prepended by the carrier. Businesses do not control this prefix. If a subscriber moves from one circle or operator to another (using MNP), the prefix changes accordingly.

7. Consent Requirements

Consent requirements in India differ by message category. The most restrictive rules apply to promotional messages; transactional messages require the least formality.

Scenario Consent Required
Transactional (-T) No explicit consent needed — the customer's own transaction (within 30 minutes) constitutes the basis. Sending OTPs, payment confirmations to customers who transact with you requires no separate consent registration.
Service Implicit (-S) Based on inferred consent from the existing customer/subscriber relationship. If someone is your customer, you may send them service messages related to that relationship without separate consent registration on DLT. However, must not include promotional content.
Promotional (-P) to Non-DND No explicit consent needed if the subscriber is not on DND and the message is sent within the promotional time window. The subscriber's absence from DND implies acceptance of promotional communication within TRAI's framework.
Promotional (-P) to DND subscribers Requires explicit digital consent recorded via DCA (Digital Consent Acquisition) — OTP-verified and registered on the DLT Consent Register. This consent overrides DND status.
Under DPDP Act (when enforced) Granular, specific, informed, freely given consent required for use of phone numbers for marketing. Existing blanket consent must be refreshed with proper notice. Consent withdrawal must be honoured immediately.

7.1  Opt-Out Requirements

  • STOP / UNSUBSCRIBE: All promotional SMS campaigns must offer and honour opt-out. Standard opt-out keyword is STOP (or START to re-subscribe).
  • Mandatory Opt-Out Mechanism (2025 Amendment): Telecom operators are now required to include a mandatory opt-out option in promotional messages (e.g., 'Reply STOP to opt out'). This is becoming a required element of all promotional templates.
  • 90-Day Re-Contact Rule: After a subscriber opts out, you may NOT send them a consent acquisition request for 90 days from the opt-out date.
  • 1909 Short Code: Subscribers can report spam to their operator by SMSing to 1909 or calling 1909. Complaints can be filed within 7 days of receiving the spam message (extended from 3 days in 2025 amendment).
  • TRAI DND App: Subscribers can also report spam via the TRAI DND mobile app.

8. Content Restrictions

8.1  Absolutely Prohibited Content

  • Firearms — promotion, sale, or instruction related to weapons
  • Gambling — any form, including online casinos, lottery, fantasy sports with financial stakes
  • Adult / sexually explicit content
  • Money / loan schemes — payday loans, unregulated lending, debt collection with threats
  • Political content or election campaign messaging
  • Religious content — proselytising or faith-based solicitation
  • Controlled substances — narcotics, cannabis, vaping
  • Alcohol — promotion of alcoholic beverages to the general public
  • Phishing and fraud — impersonation, false Sender IDs, misleading content
  • Spam — bulk unsolicited messages with no registered consent or DLT approval
  • P2P traffic via A2P paths — routing personal communications through commercial channels to evade DLT
  • Grey route / unauthorised routing — using SIM boxes or unregistered telemarketers to bypass DLT
  • OTPs or bank-branded messages sent by non-bank entities impersonating financial institutions

8.2  URL and Link Restrictions

🔗 No URL Shorteners — All Links Must Be CTA-Whitelisted

Since October 1, 2024, ALL URLs in SMS templates must be:

1. Full URLs (no public shorteners such as bit.ly, tinyurl, t.co, etc.)

2. Pre-whitelisted on the DLT platform via the CTA Whitelisting process

3. From domains you own or are authorised to use

Any SMS containing a non-whitelisted URL will be silently blocked during DLT scrubbing. This applies retroactively to previously approved templates — if you had URLs in old templates, those templates must be updated and URLs whitelisted.

8.3  OTP-Specific Rules

  • OTP messages must be sent via the Transactional (-T) category
  • OTP messages must match a registered Transactional template
  • OTP template must include the brand name
  • OTP codes must be in a tagged {#var#} variable of type 'OTP'
  • OTP validity and instruction ('Do not share') strongly recommended
  • No promotional content may be mixed into OTP messages — this reclassifies the message as Promotional and subjects it to DND/time restrictions
  • For banking OTPs: RBI mandates additional security standards (no clickable links in OTP messages per RBI advisory)

8.4  Financial Sector (BFSI) — Additional Rules

  • RBI Guidelines: OTP messages for banking and payment authentication must comply with RBI's Digital Payment Security Controls. No URLs in banking OTP messages.
  • SEBI: Capital market communications (trade alerts, portfolio updates) must comply with SEBI circular requirements on investor communication.
  • IRDAI: Insurance-related SMS must comply with IRDAI communication guidelines.
  • No Fake Bank Headers: Impersonating a bank's Sender ID is a criminal offence under the IT Act and IPC in addition to TCCCPR violations.

9. Message Encoding & Character Limits

Encoding Details
GSM-7 (Standard) 160 characters per SMS segment. Concatenated: up to 6 segments = 918 characters max. Supports standard Latin alphabet + common punctuation. Available for all routes.
UCS-2 / Unicode 70 characters per SMS segment. Concatenated: up to 6 segments = 402 characters max. Required for Hindi, Tamil, Telugu, Bengali, Kannada, Gujarati, Punjabi, Marathi, and other Indian languages. Supported on domestic DLT route (Transactional/Service). Also supported on International route.
Concatenation Support Supported with caveats — not all Sender ID types guarantee proper concatenation. Where messages are split may vary by carrier.
Indian Language Scripts All 22 scheduled Indian languages can be sent via UCS-2 encoding. Message limits are 70 characters per segment in Unicode mode.
Special Characters The following GSM-7 characters use 2 character slots: { } [ ] ^ ~ \ | €. Template length should account for this.
Template Character Limit Templates may define up to 5–6 variables. The total template length including all variables must be structured for the intended encoding. A 160-character GSM-7 template can have up to the limit, with variable content added at runtime.

10. Carrier Landscape

India has five major telecom operators (TSPs) serving over 1.18 billion mobile subscribers. Number Portability (MNP) is fully operational — subscribers can move between operators while retaining their number. The DLT platform automatically routes messages to the correct operator after portability.

Operator Details
Reliance Jio Largest operator — ~470 million subscribers. Launched 4G in 2016, rapidly became the market leader. DLT Platform: TrueConnect (trueconnect.jio.com). MCC/MNC: 404-50, 405-857, and others.
Bharti Airtel Second largest — ~380 million subscribers. India's oldest private telecom operator. Strong enterprise and B2B presence. DLT Platform: DLT Connect (dltconnect.airtel.in). MCC/MNC: 404-10, 404-20, and multiple others by circle.
Vodafone Idea (Vi) Third largest — ~225 million subscribers. Result of Vodafone-Idea merger. DLT Platform: VILPOWER (vilpower.in). MCC/MNC: 404-20, 404-30, 405-028, and others.
BSNL (Bharat Sanchar Nigam Ltd) Government-owned PSU. ~100 million subscribers. Primarily serves smaller cities and rural areas. DLT Platform: ucc-bsnl.co.in. MCC/MNC: 404-01, 404-07, and others.
MTNL (Mahanagar Telephone Nigam Ltd) Government-owned. Operates only in Delhi and Mumbai. ~3 million subscribers. DLT Platform: ucc-mtnl.in. MCC/MNC: 404-68 (Mumbai), 404-69 (Delhi).

11. Sending Best Practices

  • Always Include PE ID and Template ID in Message Payload: Both must be passed as parameters in your SMS API request for every message. Without them, messages fail DLT scrubbing.
  • Respect the Promotional Window: 10:00 AM – 9:00 PM IST strictly. Schedule campaigns to ensure even if API submission is at 8:55 PM, delivery completes before 9:00 PM.
  • Never Mix Promotional and Transactional Content: A single promotional sentence in a service/transactional message reclassifies the entire message as Promotional — triggering DND checks and time restrictions.
  • Use Full URLs Only: All URLs must be CTA-whitelisted and full-length. No public shorteners. This is now a hard network-level block.
  • Maintain Header Activity: Headers unused for 90 days are automatically deactivated. Ensure at least minimal traffic to preserve active headers, or proactively renew before dormancy.
  • Double Opt-In for Marketing Lists: Implement a confirmation step after initial opt-in. Send a confirmation SMS and activate the subscriber only when they respond affirmatively.
  • Store Consent Records: Maintain records of how and when each subscriber opted in, including channel, timestamp, opt-in wording, and any supporting evidence. Under the DPDP Act (when enforced), you will need to prove consent.
  • Include Opt-Out in Every Promotional Message: 'Reply STOP to opt out' or similar. Honour opt-outs immediately.
  • Test Templates Before Mass Campaigns: Send test messages to your own numbers before launching a large campaign to verify correct template matching and formatting.
  • Do Not Use Grey Routes: SIM-box routing and unregistered telemarketers are actively detected by TRAI's AI/ML systems and honeypots. Penalties include immediate disconnection and blacklisting.
  • Indian Language Messages: Use UCS-2 encoding for regional language content. Templates containing Indian script must be registered in the correct encoding.
  • Review Templates After Regulatory Updates: TRAI updates regulations frequently. Template categories, variable rules, and CTA requirements have all changed since 2021. Audit your template library after every major TRAI announcement.

12. Penalties for Non-Compliance

Violation Type Consequence
Unregistered Commercial SMS (UTM) Warning on first instance → Usage cap (max 20 messages/day) for 6 months on second instance → Full disconnection of all telecom resources on third/subsequent violations
Financial Disincentives (Access Providers) TRAI may impose financial penalties on TSPs for failing to act on UCC complaints or misreporting — ranging from ₹2 lakh to ₹10 lakh per instance
Blacklisting Registered Telemarketers found violating TCCCPR are blacklisted — barred from registering on any DLT platform and using any commercial communication resource
DPDP Act — Processing Without Consent (when enforced) Administrative penalty up to ₹50 crore (~USD $6 million) per instance
DPDP Act — Data Breach Failure Up to ₹250 crore (~USD $30 million) per incident
IT Act — Data Breach (current) Civil liability up to ₹5 crore; criminal liability up to 3 years imprisonment under Section 72A for wrongful disclosure of personal data
Maximum TCCCPR Penalties on Businesses Up to ₹50 lakh in fines under some interpretations; service termination for repeated violations
Grey Route Detection Immediate termination of SMS services; potential criminal liability under IT Act
Using Fake/Impersonating Sender IDs Criminal offence under IT Act and IPC — fraud, cheating, and identity theft provisions apply
Complaint Window (2025 Update) Subscribers now have 7 days (previously 3 days) to file UCC complaints. Action must be taken within 5 days against unregistered senders.

13. Pre-Launch India SMS Compliance Checklist

✅  Complete Every Item Before Sending a Single Commercial SMS in India

DLT Registration — Domestic Route

  • [ ] Determined which delivery route to use: Domestic (DLT) or International (ILDO)
  • [ ] Selected DLT platform (Airtel, Jio, Vi, BSNL, Tata, or SmartPing)
  • [ ] Completed Principal Entity (PE) registration with all KYC documents
  • [ ] Received and recorded unique PE ID (Principal Entity ID)
  • [ ] Biometric/Aadhaar OTP verification completed (per 2025 amendment)
  • [ ] All SMS Headers (Sender IDs) registered — 6-char brand-relevant headers for transactional/service, numeric for promotional
  • [ ] All Content Templates registered — correct category (Transactional / Service / Promotional / Government)
  • [ ] Brand name included in every content template
  • [ ] All variables in templates pre-tagged by type (OTP, amount, name, date, etc.) per Oct 1, 2024 mandate
  • [ ] All URLs in templates CTA-whitelisted on DLT platform (Oct 1, 2024 mandate)
  • [ ] No public URL shorteners used in any template
  • [ ] PE ID and Template ID integration confirmed with SMS provider API
  • [ ] PE-TM Binding completed with your SMS provider / CPaaS platform

Message Categories & DND

  • [ ] Every message type correctly categorised: Transactional (-T) / Service (-S) / Promotional (-P) / Government (-G)
  • [ ] Promotional messages scheduled to send only between 10:00 AM – 9:00 PM IST
  • [ ] No promotional content mixed into Transactional or Service templates
  • [ ] DND scrubbing confirmed active for promotional campaigns
  • [ ] Explicit Digital Consent (DCA) process set up if sending promotional to DND subscribers

Consent & Opt-Out

  • [ ] Opt-in consent mechanism in place for all marketing recipients
  • [ ] Consent records stored with timestamp, channel, wording, and phone number
  • [ ] STOP / opt-out keyword response configured
  • [ ] Opt-out instruction included in every promotional message
  • [ ] 90-day re-contact restriction programmed for opted-out numbers

Content & Legal

  • [ ] Prohibited content review completed: no gambling, adult, political, religious, firearms, alcohol, cannabis content
  • [ ] OTP messages contain only OTP code, brand name, and validity — no promotional content
  • [ ] Banking/fintech OTP messages comply with RBI Digital Payment Security Controls
  • [ ] DPDP Act compliance plan in place — ready for enforcement
  • [ ] Legal counsel with India telecom/privacy expertise has reviewed the programme

14. Authoritative Sources & References

14.1 TRAI — Official Regulatory Sources

14.2 DLT Platform Links

14.3 Primary Legislation

14.4 Spam Reporting

14.5 Legal & Regulatory Analysis

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India's DLT framework is genuinely one of the most complex SMS compliance systems in the world — and it's evolving rapidly. Between the 2025 TCCCPR amendments, the October 2024 CTA Whitelisting mandate, Variable Tagging requirements, the pending DPDP Act enforcement, and the five-step DLT registration process, there's a lot that can go wrong if you go it alone.

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Frequently Asked Questions

Is DLT registration mandatory for sending SMS in India?

Yes. DLT registration is mandatory for all businesses sending commercial SMS in India through domestic telecom networks. Businesses must register as a Principal Entity (PE) on an approved DLT platform and obtain approved Sender IDs (Headers) and message templates before messages can be delivered.

What regulations govern SMS messaging in India?

SMS messaging in India is regulated by the Telecom Regulatory Authority of India (TRAI) under the Telecom Commercial Communications Customer Preference Regulations (TCCCPR) 2018, which were further amended in 2025. These regulations require businesses to register on a Distributed Ledger Technology (DLT) platform, approve sender IDs (Headers), and register message templates before sending commercial SMS.

What is the DLT platform used in India's SMS ecosystem?

DLT (Distributed Ledger Technology) is the blockchain-based infrastructure used by Indian telecom operators to regulate commercial messaging. The platform maintains a registry of Principal Entities, Sender IDs, message templates, and customer consent records, and performs DLT scrubbing to validate every SMS before delivery.

What is a Principal Entity (PE) in India's DLT system?

A Principal Entity (PE) is the business or organization that sends commercial SMS messages to customers. After completing DLT registration, the business receives a unique PE ID, which must be included in every SMS API request submitted to telecom operators.

What is an SMS Header or Sender ID in India?

An SMS Header (Sender ID) is the identifier that appears as the sender of a message on a recipient’s phone. In India, headers typically contain six alphanumeric characters representing the brand name, and are displayed with a telecom prefix and category suffix such as VM-ABCDEF-T.

What are the different SMS categories under TRAI regulations?

Under the TCCCPR framework, SMS messages are classified into four categories:

  • Transactional (-T): OTPs, banking alerts, and transaction confirmations
  • Service (-S): Updates sent to existing customers about services they use
  • Promotional (-P): Marketing and advertising messages
  • Government (-G): Official government notifications

Each category has different rules regarding consent, DND filtering, and delivery timing.

What is the DND registry in India?

India maintains a National Do Not Disturb (DND) registry, also known as the National Customer Preference Register (NCPR), which allows mobile subscribers to block promotional messages. DLT platforms perform real-time scrubbing against the DND registry before delivering promotional SMS.

What are the time restrictions for promotional SMS in India?

Promotional SMS messages in India may only be delivered between 10:00 AM and 9:00 PM Indian Standard Time (IST). Transactional and service messages such as OTP alerts can be sent 24 hours a day.

What penalties apply for violating SMS regulations in India?

Violating TRAI SMS regulations can result in serious consequences including telecom resource suspension, blacklisting of telemarketers, and financial penalties. Businesses may also face liability under India’s Digital Personal Data Protection Act (DPDP Act) 2023 for unlawful processing of personal data.

What is CTA whitelisting in India's SMS regulations?

CTA (Call-to-Action) whitelisting is a requirement introduced in October 2024 under TRAI regulations. All URLs, app links, or other call-to-action elements included in SMS messages must be pre-approved on the DLT platform before they can be used.

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