To send domestic A2P SMS in India, DLT registration is mandatory: the sending business registers on a DLT (Distributed Ledger Technology) platform run by an Indian operator, first the entity, then each sender ID (header), then every message template. Messages that do not match a registered header and template are blocked during scrubbing. As of 2026, URLs, APK links and OTT links in messages must also be whitelisted.
Rules last checked: October 2026.
Sender ID registration on DLT
Commercial SMS in India falls under TRAI's Telecom Commercial Communications Customer Preference Regulations (TCCCPR). Operators enforce it through DLT platforms run by Jio, Airtel, Vodafone Idea, BSNL and others. Registering on one DLT portal is enough, because the platforms share data across networks. The process has several layers:
- Principal Entity (PE): the brand that sends the messages registers with its company documents (tax and business registration details, plus an authorization letter) and receives an Entity ID.
- Header: the sender ID, registered under the entity for a specific category.
- Content templates: every message text, with its fixed wording and declared variables, approved under a header and a category.
- Chain binding: since late 2024 the entity must also link itself on DLT to the provider (telemarketer) that delivers its traffic. If the provider changes, the chain must be updated before sending resumes.
Our general guide to sender ID registration explains why so many countries now work this way. India is the strictest example.
Header types and suffixes
| Category | Header format | Suffix shown since May 2025 | DND numbers |
|---|---|---|---|
| Transactional (banks, bank OTPs) | 6 characters | -T | Delivered |
| Service (alerts, non-bank OTPs, notifications) | 6 characters | -S | Delivered |
| Promotional | 6-digit numeric | -P | Not delivered |
| Government | Exempted headers | -G | Delivered |
Operators also add a short network and circle prefix, so a header registered as ABCDEF reaches the handset as something like VM-ABCDEF-S. You do not add the prefix or suffix yourself. Dynamic sender IDs are not supported, and a header can only carry the category it was registered for. The differences between the categories are covered in transactional vs promotional SMS.
Templates, URLs and scrubbing
Each message is checked against the registered header, the approved template and the recipient's DND preference. The fixed text must match the template exactly, so a changed word, extra space or different punctuation is enough to fail. Variables must use the declared variable tags, and the template ID has to be passed with every submission. A message that fails scrubbing is usually accepted by the API but reported as failed in the delivery report.
Since 1 October 2024, TRAI has required operators to block messages containing URLs, APKs or OTT links that are not whitelisted on DLT. Register the full domains you use, and avoid public URL shorteners, which providers report as not accepted. A separate timeline was announced for call-back numbers, so check the current rule with your provider.
DND, consent and sending hours
India keeps a national do-not-disturb register (NCPR). Promotional messages are not delivered to numbers on it and are only delivered during a daytime window. Providers commonly cite 10:00 to 21:00 IST, some cite 09:00 as the start, so confirm the window with your route. Promotional programs also need customer consent recorded on DLT. Transactional and service traffic can be sent at any hour. Gambling, adult content, loans and other sensitive categories are refused or tightly controlled; see SMS content restrictions for how operators treat them.
Mobile networks and international routes
The main mobile networks are Jio, Airtel, Vodafone Idea (Vi) and BSNL. Unicode (UCS-2) is supported, so Hindi and other Indian scripts work, but a Unicode segment holds far fewer characters; see GSM-7 vs Unicode encoding. Foreign businesses without DLT registration can only use the international route, where operators charge international termination and the sender is shown as a random numeric ID instead of a brand. Traffic from Indian entities offered through international or grey paths is a common source of blocking and fake delivery reports.
OTP traffic to India
Register OTP templates under the right category: transactional for banks, service for everyone else. Keep the brand name in the fixed text, put the code in a declared numeric variable, and never add promotional wording, which can move the message into a category that DND numbers do not receive. Test each template on all four networks before launch, as explained in how to test an SMS route, and follow our OTP SMS best practices.
VoIPMatcher sources A2P SMS routes from its carriers and manages them, and buyers and sellers never see each other. Tell us whether your traffic is DLT-registered or international, and which categories you send. See the India SMS destination page or request an India SMS route.
Frequently asked questions
Can I send SMS in India without DLT registration?
Not as domestic A2P traffic. Messages that do not match a registered entity, header and template are blocked during scrubbing. Foreign businesses without DLT registration can only use the international route, where operators charge international termination and the sender appears as a random numeric ID. Offers to send domestic traffic without DLT are grey routes and get blocked.
Is DLT registration mandatory for OTP?
Yes. OTP messages need a registered header and template like any other domestic A2P SMS in India. Register them under the transactional category for banks and the service category for everyone else, keep the brand name in the fixed text, put the code in a declared numeric variable and never add promotional wording.
What is a DLT template ID?
A DLT template ID is the identifier a DLT platform assigns to an approved message template. It has to be passed with every submission, together with the registered header, so the operator can check the message against the template during scrubbing. A message without the right template ID, or with text that does not match, fails.
How many DLT portals do I need to register on?
One is enough. DLT platforms are run by Jio, Airtel, Vodafone Idea, BSNL and others, and they share registration data across networks. Register your entity, headers and templates on one portal, then link your entity to the provider that delivers your traffic. If you change provider, update that chain binding before sending resumes.
Why does my DLT SMS show as failed?
A message that fails DLT scrubbing is usually accepted by the API but reported as failed in the delivery report. Common causes are fixed text that differs from the template by a word, space or punctuation mark, a missing or wrong template ID, a URL that is not whitelisted, or a promotional message sent to a DND number.
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