If you send SMS in India, one of the first decisions you will face is whether your message is promotional or transactional. This is not a minor label, it determines the DLT route, the sender ID format, whether DND-registered numbers receive the message, and the hours during which it can be delivered. Getting this wrong leads to blocked messages or compliance violations. Here is a clear breakdown.
What Counts as Transactional SMS
Transactional SMS carries information the recipient needs as a direct result of an action or an existing relationship. There is no marketing intent. Classic examples include OTPs for login or payment, bank balance alerts, order confirmations, delivery updates, appointment reminders, and ticket bookings. Because these messages are essential, they are delivered even to numbers registered under DND, and they can go out 24x7 without time restrictions. They use numeric or alphanumeric sender IDs tied to a service-implicit or service-explicit content category on DLT. Our OTP SMS service runs entirely on transactional routes for maximum speed and reach.
What Counts as Promotional SMS
Promotional SMS is sent to push a product, offer, discount, or brand message to prospects and customers. Think festival sale alerts, new product launches, and discount codes. Promotional messages are governed more tightly: they are not delivered to DND-registered numbers (unless the user has opted in), and they can only be sent within the permitted daytime window, generally 9 AM to 9 PM. Promotional SMS uses a 6-character alphanumeric sender ID. To run effective promotional campaigns within these rules, see our bulk SMS platform.
The DLT Routes Behind Each Type
Under TRAI's DLT framework, message content is categorised so operators can apply the right rules. The common content categories are:
- Service Implicit - transactional messages triggered by a customer action, such as an OTP or order confirmation. Delivered 24x7, reaches DND numbers.
- Service Explicit - service messages that need explicit consent, such as account-related notifications that border on informational marketing.
- Promotional - pure marketing content. Restricted to non-DND numbers and the 9 AM to 9 PM window.
- Government - messages from registered government entities.
Every template you register on DLT is tagged with one of these categories, and the operator routes and filters your traffic accordingly. Mismatching content to category is a top cause of message rejection.
Sender ID Types and Time-Window Rules
The sender ID (also called the header) tells the recipient who sent the message. Promotional traffic uses a 6-character alphanumeric header. Transactional and service traffic typically uses a header that maps to your registered brand. The time-window rule is strict: promotional content cannot be delivered outside the daytime promotional window, while genuine transactional content like OTPs flows around the clock. Sending a discount disguised as a transactional alert is a compliance risk and operators actively filter for it. For a deeper explanation of headers, read our guide to sender IDs and the SMS API.
Real-World Examples
A few concrete cases make the distinction obvious:
- Transactional: Your OTP for login is 482913. Valid for 10 minutes. Do not share it. (OTP, sent any time, reaches everyone.)
- Transactional: Your order has been shipped and will arrive by Friday. (Order update, essential information.)
- Promotional: Flat 30% off this weekend. Shop now and save big. (Marketing, daytime only, non-DND numbers.)
- Service Explicit: Your premium subscription renews next week. Manage it in your account. (Informational, consent-based.)
Retailers and e-commerce brands often need both types: transactional for order and delivery flows, promotional for sale campaigns. See how we support these mixed needs on our retail and e-commerce solutions page.
How to Choose the Right Route
The rule of thumb is simple: if the message is something the customer expects or needs because of an action they took, it is transactional. If you are trying to influence a purchase or build awareness, it is promotional. When in doubt, register separate templates for each purpose so you stay compliant. Mixing marketing language into a transactional template is the fastest way to get a template rejected on DLT or filtered by the operator. A compliant provider like Guru SMS, with 230+ direct operator connections and 98-99% transactional delivery, ensures each message takes the correct route.
Frequently Asked Questions
Can transactional SMS be sent at night?
Yes. Genuine transactional messages such as OTPs and order alerts are delivered 24x7 with no time-window restriction, because they carry information the recipient needs immediately.
Will promotional SMS reach DND-registered numbers?
No. Promotional messages are not delivered to numbers on the DND list unless the user has explicitly opted in. This is enforced by operators under TRAI rules.
What is the promotional time window in India?
Promotional SMS can generally be delivered only between 9 AM and 9 PM. Sending marketing content outside this window will result in the messages being blocked.
Can I use one sender ID for both types?
It is best practice to register and use separate headers and templates for promotional and transactional traffic. This keeps your content categorised correctly on DLT and avoids rejection or filtering.
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