If your business sends bulk SMS in India, compliance is not optional. The Telecom Regulatory Authority of India (TRAI) enforces a strict framework built on the Distributed Ledger Technology (DLT) platform, and every message that reaches an Indian mobile number passes through these checks. Understanding the rules protects your sender reputation, keeps your campaigns running and helps you avoid heavy penalties. This guide explains the core pillars of SMS compliance in plain language.
What is DLT and why it exists
DLT is a blockchain-based registration system mandated by TRAI under the Telecom Commercial Communications Customer Preference Regulations (TCCCPR), 2018. It was introduced to curb spam, prevent header spoofing and create an auditable trail for every commercial message. Operators such as Jio, Airtel, Vi and BSNL run DLT portals where businesses register before sending any commercial SMS.
Registration involves four building blocks. First, an entity (your business) registers with a verified PAN or GST. Second, you register a sender ID, also called a header, which is the six-character alphanumeric code that appears as the sender. Third, you register message templates, since free-form commercial SMS is not permitted. Fourth, you map consent and your communication purpose. At Guru SMS we help our 500+ clients complete this entire onboarding correctly the first time, because a rejected header or template can stall a launch by days.
Message categories that decide your route
TRAI classifies commercial SMS into distinct categories, and the category determines the route, the timing rules and the DND treatment.
- Transactional: triggered by a customer action, such as OTPs and bank alerts. These are delivered around the clock and are not blocked by DND.
- Service-explicit and service-implicit: relationship messages where the customer has an existing service with you, like order updates and ticket confirmations.
- Promotional: marketing and offers. These are subject to DND preferences and time windows.
Choosing the right category matters. Sending a promotional message on a transactional header is a violation. Our OTP SMS service uses a dedicated transactional route to guarantee the 98-99% delivery our clients rely on.
DND and consent: the heart of the rules
The Do Not Disturb (DND) registry lets subscribers block promotional communication, either fully or by category and time band. Before you send a promotional campaign, the DLT scrubbing layer checks each number against these preferences and filters out anyone who has opted out. This happens automatically on a compliant platform.
Consent is the second guardrail. Under TCCCPR, you must hold verifiable, explicit consent before sending promotional messages, and you must be able to produce the consent record on demand. Pre-checked boxes and inferred consent are risky. The cleanest approach is a documented opt-in, such as a customer ticking a clear checkbox or replying to a consent SMS, with the timestamp and source stored.
Promotional time windows
TRAI restricts promotional SMS to specified hours. Telemarketing and promotional messages are generally permitted between 9:00 AM and 9:00 PM, and sending outside this window is a compliance breach. Transactional and essential service messages, including OTPs, are exempt because customers expect them at any hour. If you run a marketing campaign, schedule sends within the permitted window. A good platform enforces this automatically so a mistimed broadcast never goes out.
Penalties for violations
Non-compliance carries real consequences. Operators can impose financial penalties on registered entities and telemarketers, blacklist offending headers, suspend templates and even deregister persistent violators from the DLT ecosystem. Repeated complaints against a header can trigger usage-cap reductions, meaning your daily sending volume gets throttled. The reputational and operational cost of losing your sender ID often exceeds any fine. This is why working with a TRAI-registered partner who pre-validates every template and header is the safest path.
A practical compliance checklist
- Register your entity, header and templates on the DLT platform before going live.
- Map each message to the correct category and route.
- Collect and store explicit, timestamped consent for all promotional sends.
- Respect the 9 AM to 9 PM window for promotional traffic.
- Keep transactional traffic on a dedicated transactional route.
- Monitor delivery reports and complaint ratios continuously.
Explore our full range of messaging services and our bulk SMS platform, both built around this compliance framework. Regulated sectors such as banking and finance face the strictest scrutiny, and we design their routing accordingly.
Frequently Asked Questions
Is DLT registration mandatory for every business sending SMS?
Yes. Any entity sending commercial SMS to Indian mobile numbers must complete DLT registration with entity, header and template approval. Without it, your messages will not be delivered through operator networks.
Can I send OTPs at night despite DND?
Yes. OTPs are transactional messages triggered by a customer action. They are exempt from DND and from promotional time windows, so they are delivered around the clock.
What happens if my SMS template is not approved?
Messages that do not match an approved template are rejected by the operator before delivery. You must register the exact template, including variable fields, and use it precisely as approved.
How long does DLT registration take?
Entity registration is often same-day, while header and template approvals can take a few hours to a couple of days depending on the operator. Working with a registered aggregator like Guru SMS speeds this up significantly.
Ready to send fully compliant SMS without the guesswork? Talk to the Guru SMS team and we will handle DLT registration, routing and approvals end to end. Reach us at our contact page or call +91-9853084604 to get started today.