DLT rules for SMS marketing in India: what gets you blocked

Short answer: Commercial SMS in India must go through a registered sender name (header) and pre-registered message wording (content template) on the operators’ DLT platform, under TRAI’s Telecom Commercial Communications Customer Preference Regulations, 2018. The February 2025 amendment added sender-name suffixes, a mandatory opt-out in promotional messages, consent that expires, and a lower complaint trigger of five complaints in ten days. So register for the messages customers expect, and be sparing with offers.

Most small businesses meet DLT as a wall. The SMS tool says “sent”, nothing arrives, and nobody can say why. The registration is not hard to understand, but it has more moving parts than a WhatsApp template, and the 2025 changes made the penalty for getting it wrong much sharper.

This guide covers what TRAI’s DLT rules ask of you, what changed, and a position you may not expect: for most small businesses, SMS should do a narrow job, and promotional SMS is the part to be careful with. It sits under our wider guide to marketing automation for small businesses in India, which covers the channel order and the DPDP consent side. This is not legal advice, so confirm current rules with your operator or a qualified adviser.

Who has to register, and who can skip SMS altogether

If you send commercial SMS in bulk, you need DLT registration. That covers order alerts, payment reminders and OTPs as much as offers.

If your customers only reach you and hear from you on WhatsApp, you do not need it, because WhatsApp Business messaging is outside the DLT regime. It runs on Meta’s own opt-in and template rules instead. Our view: if your customers answer on WhatsApp, SMS is a second channel, not the first. Build the WhatsApp flow, then decide whether SMS earns its place.

Sending offers from a personal SIM is not a shortcut. It is exactly the behaviour the rules and the complaint system are aimed at. Senders are not allowed to use normal 10-digit numbers for telemarketing, and a personal number blasting a list is the standard example.

The three things you register: yourself, your sender name, your wording

DLT registration has three layers. You register the business itself, which TRAI calls the principal entity. You register a sender name, called a header. And you register each message template, meaning the exact wording, with blanks for the parts that change per customer, such as a name or an order number.

Your SMS provider sits between you and the operator. TRAI’s term for that middle party is a telemarketer. The rules limit the number of intermediaries between the principal entity and the telemarketer, so that every message can be traced back to the business that sent it. If your provider resells another provider’s route, ask how many steps sit between you and the operator.

Registering a sender or telemarketer involves physical verification, biometric authentication and linking a unique mobile number. Operators may also prescribe a security deposit for senders and telemarketers, which can be forfeited for violations, and they must sign a legally binding agreement with each registered sender setting out roles and the action that can be taken. Fees, deposits and approval times vary by operator, so they are a question for your provider, not something this guide can quote.

Language matters too. Each language needs its own registered template. Indian-script SMS sends as Unicode at roughly 70 characters per billed part against about 160 for plain English, a point we cover in our comparison of marketing automation platforms in India. A Hindi version of your delivery alert is a separate template with a separate approval.

Promotional, service or transactional: the label decides everything

In plain terms, a promotional message is an offer or an advertisement. Transactional and service messages relate to something the customer has done or bought: an OTP, an order, a delivery, a payment, an appointment. The label is not something you change from one send to the next. The category is fixed when the template is registered with the operator, so register honestly, and ask your provider which category the operator will accept for each message.

The label matters because of what happens when you blend them. Khaitan & Co’s summary of the amendment says that if promotional content is mixed with any other type of communication, the whole communication is treated as promotional. In practice: never put “10% off your next order” in a delivery alert. The moment you do, your delivery alert is a promotional message, with everything that follows from that: the opt-out line, the consent rules and the complaint risk.

Keep the jobs separate. Alerts carry facts about the thing the customer did. Offers are sent as their own message, to people who agreed to hear about offers.

What the letter after your sender name tells your customer

Under the February 2025 amendment, sender names now carry a suffix so the customer can tell what kind of message they are reading: -P for promotional, -S for service, -T for transactional and -G for government. The details are in TRAI’s press release of 12 February 2025, which also describes the framework as blockchain-based.

Think about what the customer sees. A message from your shop that ends in -P is, to them, an advertisement. If the text is dressed up as an order update but the sender name says promotional, the mismatch is visible. People who feel tricked complain, and complaints are what the whole system now runs on. The rules also class any message sent to deceive, or attempt to deceive, customers as unsolicited commercial communication.

Consent now has an expiry date

The amendment did more than relabel messages. It put time limits on consent, and these are the ones to plan around.

Promotional messages must carry a mandatory option for the customer to opt out. If a customer does opt out, you must not ask for consent again until ninety (90) days after the opt-out. The customer can opt back in at any time, but you cannot chase them. Treat those 90 days as a quiet period.

Consent given for completing an ongoing transaction is valid only for 7 days. TRAI’s stated reason is that businesses should not keep calling or messaging indefinitely on the pretext of earlier consent. In practice: an enquiry is not a licence to message someone for months.

Consent that is implicit in transactional and service communication is valid only for the duration or discharge of the contract between the customer and you. Once the job is finished, that implicit consent ends, and explicit consent is needed for anything further.

DLT consent and DPDP Act consent are separate records. Holding one does not give you the other. The DPDP side, including how to word an opt-in, is covered in the marketing automation guide, so we will not repeat it here.

Why a link can get an approved template rejected

Here is a cause of “it worked last month” that catches many senders. In its press release of 18 November 2025, TRAI directed access providers to mandate pre-tagging of all variable components in SMS content templates. Variable components are the parts that change from recipient to recipient while the rest of the text stays fixed: URLs, app download links and callback numbers.

At registration, you tag each variable to say what it will hold. TRAI’s example is that tagging a variable as #url# means it contains a URL. The purpose is to let operators check the inserted value against whitelisted domains, numbers or links. TRAI’s press release of 18 November 2025 gave access providers and principal entities 60 days to modify existing templates. After that, in TRAI’s words, “messages sent using non-compliant templates will be rejected and not delivered.”

That window has passed. If you have a payment-link or tracking-link template that was registered before then and never updated, it is a likely cause of a sequence that quietly stopped. We tell the wider story of silent drops in our guide to AI lead generation in India. The fix here is specific: ask your provider whether every variable in every live template is tagged.

Five complaints in ten days: how a sender gets cut off

This is the part that should change how you plan. Customers can now complain about spam from unregistered senders without first registering their preferences. The window to complain is 7 days from receiving the message, up from 3 days. Access providers must act against unregistered senders within 5 days, previously 30.

The trigger for action against a sender was tightened from 10 complaints in the last 7 days to “5 complaints against the sender in last 10 days”. For a large sender, five complaints is noise. For a business with a list of a few hundred, a single badly judged festival blast to people who barely remember you can reach it.

The consequence is not a fine on you. For a first violation of the regulatory threshold, outgoing services of all your telecom resources are barred for 15 days. For subsequent violations, all your telecom resources are disconnected across all access providers for one year and you are blacklisted. The release does not spell out how each step applies to a registered sender as against an unregistered one, so ask your provider how complaints against your sender name are counted.

The money figures in the release, ₹2 lakh for a first instance, ₹5 lakh for a second and ₹10 lakh per instance after that, fall on access providers, the telecom operators, for misreporting the count of unsolicited communication. They do not fall on the business sending. Your penalty is losing the ability to send, and for a business that relies on delivery alerts, that is the one that hurts.

So for a small list, the real compliance tools are frequency and relevance. Send fewer offers. Send them only to people who agreed. Make the opt-out line work. Do not message a customer about something they never asked about.

A Rajkot kitchenware distributor, worked through (hypothetical)

This is an illustration, not a client. A kitchenware distributor in Rajkot supplies retailers. They want two things: dispatch and payment-due messages to retailers, and a festive-season offer to past buyers.

What gets registered as what. The business registers as the principal entity. Dispatch and payment-due messages are registered as service or transactional templates, whichever category the operator accepts for them, because each relates to something the retailer ordered. Because Gujarati-speaking retailers prefer their own language, the distributor registers a Gujarati version of each as a separate template.

Where the offer goes. The festive offer is promotional. It gets its own promotional template, so it arrives with the -P suffix, and it carries the mandatory opt-out option. It goes only to retailers who agreed to hear about offers, not to everyone who has ever placed an order.

The old template. The distributor’s dispatch alert includes a tracking link, and the template predates the November 2025 direction. The link variable now needs the #url# tag. Until it is re-registered with the tag, the alert is a candidate for rejection, which would look to the distributor like retailers simply not receiving dispatch news.

What they decide not to do. No offer line goes inside a dispatch alert, because that would make the whole message promotional. And a retailer who opted out of a previous offer is not asked for consent again for 90 days.

Nothing in this setup needs a large list or a clever tool. It needs a handful of templates and a discipline about which message goes where.

When SMS is not worth registering for

Say no where it is no. SMS is probably not worth the registration if you have fewer than a few hundred contacts who all use WhatsApp. It is not worth it if nobody in the business will maintain templates and handle the annual self-certification. Per Khaitan & Co, registered senders and telemarketers must self-certify their registration details, headers and content templates every year. A neglected registration is a liability. And it is not worth it if all you want to do is send offers, because offers are the riskiest thing you can send.

SMS is worth it for OTPs and for payment or delivery messages that must arrive. It is worth it for customers on feature phones or not on WhatsApp, and as a fallback when a WhatsApp message goes undelivered. That is the narrow job: messages customers expect, to people who cannot be reached another way.

A note on calls, since people mix them up. For voice calls, the 140 series is for promotional calls and the 1600 series for transactional and service calls. We cover that in our guide to AI voice agents for lead follow-up in India.

What to ask your SMS provider before you sign

A good provider answers these without hesitation. A vague answer to any of them is information.

• What are the registration fees and any security deposit, and when is the deposit forfeited?
• How long does template approval usually take with each operator?
• Who registers and edits templates, you or the provider?
• What are the permitted hours for promotional sends right now, and does the platform enforce them?
• How are opt-outs recorded, and how do they sync across every list you send to?
• Is every variable tagged at registration, including links and callback numbers?
• Do you register separate templates for each language, and how is billing counted for Indian scripts?
• Can you see delivery reports by template, so a single rejected template does not hide inside a total?

Promotional sending is restricted to permitted hours. Confirm the current window with your operator or provider before you schedule anything.

If you would like help sorting out which of your messages belong on SMS, which on WhatsApp and which nowhere, that is part of our AI automation work.

Frequently asked questions

Do I need DLT registration to send SMS to my own customers? Yes, if the message is commercial and goes out as bulk SMS. Your business, your sender name and the exact wording of each message are registered on the operators’ DLT platform before anything is delivered. Offers sent in bulk from a personal SIM are exactly what the rules and the complaint system are aimed at. Ask your operator or provider about any grey area.

What do -P, -S, -T and -G mean after an SMS sender name? TRAI’s February 2025 amendment added a suffix to sender names so customers can tell the message type: -P for promotional, -S for service, -T for transactional and -G for government. The customer sees what you registered as, so an offer sent under a service or transactional name looks out of place. The category is fixed when the template is registered with the operator.

Can I add an offer to an order or delivery SMS? Do not. According to Khaitan & Co, if promotional content is mixed with any other type of communication, the whole communication is treated as promotional. Your delivery alert would then be promotional, with the opt-out option and the consent that come with it. Send the offer as its own promotional message, to people who agreed to receive offers.

How long does a customer’s consent last under TRAI’s rules? It depends on the kind. Consent given to complete an ongoing transaction is valid for only 7 days. Consent that is implicit in transactional and service messages lasts only for the duration or discharge of the contract, and after that explicit consent is needed. If a customer opts out, you cannot ask for consent again until 90 days have passed.

What happens if customers complain about my SMS? Customers can complain within 7 days of receiving a message. The trigger for action is now 5 complaints against a sender in 10 days. For a first violation, outgoing services on all the sender’s telecom resources are barred for 15 days. Later violations can mean disconnection across all access providers for one year and blacklisting.

Is WhatsApp covered by the DLT rules? No. WhatsApp Business messaging sits outside the DLT regime and runs on Meta’s own opt-in and template rules. That does not make it a free pass: you still need proper consent, and DPDP consent and DLT consent are separate records. Treat WhatsApp as its own compliance job with its own templates and its own opt-ins.

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Not sure which of your SMS templates would survive the 2025 rules? Get a free marketing audit and we will tell you plainly what to fix first.