Short answer
Under TRAI's TCCCPR rules and operator DLT platforms, an SMS is classified by its content and registered template category, not by the label a business prefers. Wrong category, mixed promotional wording, or a template mismatch leads to scrubbing, failed delivery and, for repeated misuse, template blacklisting or traffic suspension.
Indian commercial SMS runs through Distributed Ledger Technology (DLT) platforms operated by telecom access providers. Headers, templates and consent are checked before delivery. This guide compares Transactional (-T), Service (-S) and Promotional (-P) categories after the 2025 amendments, including what happened to the older "Service Explicit" label. For the full registration flow, see the DLT registration guide.
1. Quick comparison
| Feature | Transactional (-T) | Service (-S) | Promotional (-P) |
|---|---|---|---|
| Primary purpose | OTPs and other messages tied to a customer-started transaction (within the rules for that category) | Account and service updates for an existing customer relationship, and messages that help complete a purchase underway | Marketing, offers, launches and other commercial promotions - including traffic that used to sit under Service Explicit |
| Typical trigger | Customer action that starts a transaction (for example login OTP or payment confirmation) | Ongoing service or purchase journey for an existing customer | Sender-initiated campaigns |
| Consent / preferences | No explicit consent required; customers cannot opt out of these | Inferred consent for existing customers; explicit consent for an ongoing purchase is time-limited (seven days under the amended rules) | Follows customer preferences unless you hold recorded explicit consent; each message must include a way to opt out |
| Header suffix | -T (added by the operator at scrubbing) | -S | -P |
| Delivery timing | Used for time-sensitive traffic such as OTPs; confirm current operator practice for your templates | Confirm permitted windows with your operator for each template type | Commercial promotional traffic is limited to permitted hours; industry practice commonly cites 10:00 AM to 9:00 PM - always confirm on your DLT portal and with your provider |
Government (-G) is a separate category for messages sent on the direction of Central or State Government (or an agency authorised by TRAI). It is outside the commercial T / S / P comparison above.
2. Transactional (-T) and Service (-S)
Transactional SMS (-T)
Transactional templates cover messages sent within 30 minutes of a transaction the customer started - for example OTPs for bank and non-bank logins, transaction confirmations and refund information.
- Two-factor authentication and OTP codes
- Payment, order or refund confirmations that meet the transactional definition on your portal
Service SMS (-S)
Service templates cover information for existing customers about a product or service they use - for example delivery updates, warranty or recall notices and periodic balance alerts - and messages that help complete a purchase the recipient is making.
- Shipping and fulfilment updates
- Safety, warranty or recall notices
- Service status that is not marketing copy
No promotional wording on T or S routes
These categories cannot carry marketing content. Adding a discount line, sale offer or similar promotional footer can cause the message to be treated as promotional. Mixed content is a common reason for failed delivery and category misuse findings. See why SMS delivery fails.
3. Promotional SMS (-P)
Promotional traffic covers marketing and offers. Any message that mixes promotional content into another type is treated as promotional.
- Seasonal offers, flash sales and marketing newsletters
- Product launches and event invitations
Service Explicit migration. Under the newer definitions, marketing sent on the basis of explicit consent counts as promotional. Several SMS providers report that operators moved templates from the former "Service Explicit" category into Promotional (-P). Those templates then follow promotional consent, opt-out and timing rules. Check the categories shown on your operator portal before submitting or migrating templates.
4. Core compliance rules
- Header suffixes: Operators add -T, -S, -P or -G to the header when the message is delivered so customers can see the type. You do not type the suffix into the template yourself.
- Exact template matching: Fixed text must match the approved DLT template. Only registered variables may change. Use typed tags such as
{#numeric#},{#alphanumeric#}and{#url#}- not the old generic{#var#}. Details are in the TRAI DLT variable tagging guide. - No mixed content: Do not attach a promotional offer or marketing link to a transactional or service alert. Wrong-category templates can be blacklisted; repeated misuse can lead to traffic suspension.
- Consent and opt-out: For promotional (and consent-based) campaigns, keep accurate opt-in records and include the opt-out method your portal requires.
- PE-TM chain and whitelisting: Declare your SMS provider chain, and whitelist URLs and callback numbers before you use them in templates.
Always confirm templates and categories on your operator DLT portal (Jio, Airtel, Vi or BSNL) before production traffic.
Need help classifying templates?
SMSTAKE offers free DLT registration support to any Indian business - entity, headers, templates and PE-TM chain guidance. Operator fees and approvals remain with the operator portals.
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