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4. SMS Compliance in India
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4.1 The regulatory bodies that govern SMS in India
TRAI (Telecom Regulatory Authority of India)
TRAI is the sole regulator for commercial SMS in India. It writes and enforces the rules governing,
- Consent
- Sender registration
- Message categorization
- Complaint handling
It can order telecom operators to suspend or disconnect non-compliant senders.
TCCCPR 2018 (as amended)
The Telecom Commercial Communications Customer Preference Regulations, 2018 is the core regulation. It replaced the earlier 2010 framework and introduced the current blockchain-based registration system. TRAI amended TCCCPR again in February 2025 to tighten consent rules and extend consumer complaint windows, with a further draft amendment issued in March 2026.
Telecom operators as DLT administrators
Jio, Airtel, Vodafone Idea, and BSNL each have a Distributed Ledger Technology (DLT) platform as mandated by TRAI. Registration on any one operator's DLT portal is shared across the common registry, but each operator still checks every message against the DLT records before allowing it to be delivered.
4.2 DLT registration: The foundation of SMS compliance in India
No commercial SMS reaches an Indian number without passing DLT registration first.
This has four parts:
- Principal Entity (PE) registration: your business registers with a telecom operator using PAN, GST, and incorporation documents. This produces a Principal Entity ID (PEID), your permanent identity across all operators.e recipient has to have clearly agreed to receive marketing messages. This could be through a sign-up form, a checked consent box, a verbal agreement, or another explicit opt-in method. The terms of consent must be clear and available to the recipient when they give their permission.
- Header (Sender ID) registration: the 6-character name that appears in the "From" field (for example, ZEPICM or SWIGGY). Headers are case-sensitive and must be registered under the same legal entity as the PEID.
- Template registration: the exact text of every message you intend to send, including variable fields (like OTP or order number), submitted for approval against the header's category.
- Consent template registration: the specific wording used to capture consent from a recipient, recorded and tied to the principal entity.
Operators block every outbound message against this registry. Content that doesn't match an approved template is blocked automatically.
Message categories and what each one allow
TRAI recognizes four active commercial message categories. Suffixes are automatically assigned to headers by the telecom operators during the DLT scrubbing phase based on template registration.
Category
Suffix
Consent Needed?
Reaches DND Numbers?
Sending Window
Transactional
-T
No
Yes
24/7
Service Implicit
-S
No (Inferred from active contract)
Yes
24/7
Promotional
-P
Yes (Via DCA for DND numbers)
No, unless explicit DCA
opt-in exists
10:00 AM
to 9:00 PM
Government
-G
No
Yes
24/7
The historical "Service Explicit" category has been dissolved. Mixing promotional, marketing, or cross-sell lines into a service message automatically forces the template into the Promotional (-P) category.
Variable tagging & Whitelisting rules
Generic variable slots are no longer permitted in DLT templates. Senders must explicitly pre-declare the data type of every variable slot using specific formatting:
- #number#: Reserved strictly for numeric OTPs, account digits, or monetary amounts.
- #url# — Used for standard web links. The target domain must be pre-whitelisted on the DLT portal.
- #cbn# — Used for Call-Back Numbers. The telephone number must be verified and owned by the principal entity.
If an outbound SMS contains a web link, app link, or phone number that deviates from the pre-declared tag or is missing from the DLT whitelist, the operator's gateway rejects it instantly without a delivery error to the user.
4.3 Is Two-Way SMS possible in India?
Standard bulk SMS in India is designed for one-way communication, not two-way conversations, regardless of the platform or SMS provider you use.
- Promotional SMS uses numeric sender IDs assigned by telecom operators. If a customer replies, the message usually doesn't reach your business.
- Transactional SMS uses your brand name as the sender ID (an alphanumeric header). Since these sender IDs aren't real phone numbers, customers can't reply to them.
As a result, standard DLT-registered SMS campaigns don't support inbound replies.
If you need customers to reply via SMS, you'll need a registered long code (a virtual phone number). Long codes support two-way messaging but are typically used for specific use cases such as surveys, feedback collection, keyword-based campaigns, or lead generation, not large-scale conversational marketing.
This is also why "reply STOP to opt out" isn't the primary opt-out mechanism in India the way it is in the US or Australia. TCCCPR's actual opt-out path runs through the centralized National DND registry (dial or SMS 1909, or the TRAI DND app), not through direct replies to a brand's promotional header.
Practical takeaway: for a marketing program that needs two-way conversational engagement in India, most brands use the WhatsApp Business API rather than SMS.
SMS consent requirements in India
TCCCPR recognizes two forms of consent, both tightened by the February 2025 amendment:
- Explicit consent: The recipient clearly agrees to receive marketing messages from a specific business for a specific purpose. If the recipient's number is registered on the National DND list, businesses must collect this consent through TRAI's Digital Consent Acquisition (DCA) process. This involves an OTP-verified opt-in that's recorded on the DLT Consent Register.
- Inferred consent: This is based on an existing customer relationship. However, since the February 2025 amendments, inferred consent is valid only while that relationship remains active. Once the relationship ends, the consent no longer applies.
The same amendment extended the consumer complaint window from 3 days to 7 days, giving recipients more time to report unsolicited messages after the fact.
4.4 The National DND registry (NCPR) and time restrictions
The National Customer Preference Register (NCPR), commonly called the DND registry, lets subscribers block commercial communication entirely or selectively by category (banking, real estate, education, health, consumer goods, communications/entertainment, and tourism).
- Promotional and Service Explicit messages are blocked outright for numbers on the DND registry, unless the sender holds valid DCA-based explicit consent for that specific subscriber.
- Transactional, Service Implicit, and Government messages always reach DND-registered numbers.
- Promotional and Service Explicit messages may only be sent between 10:00 AM and 9:00 PM IST, every day of the week, including weekends and public holidays. Messages submitted outside this window are rejected automatically by the DLT system.
Penalties and enforcement
Enforcement uses carrier-side AI/ML pattern analysis to find unregistered commercial telemarketing and grey-route traffic. The penalty system relies on a severe, escalating structure:
- First violation: formal warning.
- Second violation: messaging capped at a maximum of 20 messages per day for 6 months.
- Third violation: full disconnection of all telecom resources and blacklisting from every DLT platform across all operators.
Beyond this framework, TRAI actively monitors for grey-route traffic (SIM-box-based sending that bypasses DLT), using automated detection systems, and treats it as a serious violation independent of the standard escalation path.
SMS compliance checklist for India
Complete Principal Entity registration before sending any commercial SMS, under the exact legal entity name on your PAN and GST records.
Register every sender ID (header) you intend to use, and register a matching template for each one.
Assign the correct category suffix, Transactional, Service Implicit, Service Explicit, or Promotional, to every header.
Keep promotional content out of Transactional and Service Implicit messages.
Scrub every promotional and Service Explicit send against the National DND registry before sending.
Capture explicit, DCA-verified consent before sending promotional messages to any DND-registered number.
Treat inferred consent as valid only for the life of the underlying customer relationship.
Schedule all Promotional and Service Explicit sends within the 10 AM to 9 PM IST window.
Never route traffic through unregistered or grey-route senders.
Don’t rely on “reply STOP” as your primary opt-out path. Point recipients to the National DND registry (1909 or the TRAI DND app), or use a registered long code if you need genuine reply-based opt-out.
Monitor UCC complaint volume against your Principal Entity to stay ahead of the escalation framework.
4.5 FAQs
1. Can brands run two-way SMS conversations with customers in India?
Not through standard promotional or transactional headers. Those are one-way by design: promotional headers are pooled numeric codes, and transactional headers are alphanumeric with no real number behind them to route a reply. Two-way messaging requires a separate registered long code, and it's typically used for narrow cases like surveys or lead capture rather than full conversational marketing.
2. Do I need to register with TRAI before sending marketing SMS in India?
Yes. Every commercial SMS sender must complete DLT registration, covering the Principal Entity, sender ID, and message template, before sending.
3. Can I send promotional SMS to a number on the DND registry?
Only if you hold explicit, DCA-verified consent from that specific subscriber. Without it, promotional and service-explicit messages are blocked outright.
4. What hours can I send promotional SMS in India?
Between 10:00 AM and 9:00 PM IST every day, including weekends and public holidays. Transactional, service-implicit, and government messages have no time restriction.
5. What happens if my messages don't match a registered template?
They're blocked automatically by the operator's DLT scrubbing system. There's no delivery and no visible error to the recipient.
