What is DND in SMS? India’s Do-Not-Disturb Register Explained

Anyone who has registered for DND in India knows it as “the thing that makes loan-pitching SMS stop arriving.” For developers shipping SMS-driven products, DND is a piece of telecom regulation that interacts in subtle ways with OTP, transactional and promotional SMS — and getting it wrong invites TRAI penalties.

This explainer covers what DND is, the categories, how it overlaps (or doesn’t) with OTP delivery, how to check a number’s DND state, and the practical playbook for staying compliant.

DND — Definition

DND (Do Not Disturb) in the Indian telecom context refers to the National Customer Preference Register run under TRAI’s TCCCPR (Telecom Commercial Communications Customer Preference Regulations) framework. Subscribers can register their phone number to block specific categories of unsolicited commercial communication.

DND is enforced at the network level: telcos check the DND state of every recipient before delivering commercial messages. If the message category is blocked for that subscriber, the message is silently dropped (scrubbed).

DND Categories

Subscribers can choose to block messages by category, allowing some types while blocking others. The standard categories:

• 1. Banking / Insurance / Financial products
• 2. Real estate
• 3. Education
• 4. Health
• 5. Consumer goods and automobiles
• 6. Communication / Broadcasting / Entertainment / IT
• 7. Tourism and leisure
• 8. Food and beverages

Subscribers can also choose “Block all promotional” (full DND). Service / transactional categories are governed separately and cannot be blocked unilaterally by subscribers.

How DND Affects OTP vs Promotional SMS

• OTP / transactional SMS — registered under the DLT framework as service-implicit or transactional, these are not blocked by DND. The user initiated the transaction; the OTP is functional, not promotional.
• Service-explicit SMS — promotional content sent to users who have explicitly opted in. Subject to the granular DND category preferences.
• Promotional SMS — generic marketing. Always subject to full DND.

See our breakdown of transactional vs promotional SMS in India for the registration details.

Checking DND Status

Apps almost never need to query DND state directly because the operator does the check at delivery time. But if you must:

• TRAI publishes a national DND check tool at nccpregistry.gov.in.
• Some SMS providers expose a check-DND API for bulk validation.
• For OTP and transactional volume, just rely on the operator-side enforcement and monitor delivery rates per provider.

Penalties for Violating DND

TRAI has published a sliding-scale penalty matrix:

• First offence: warning + Rs 1,000 fine.
• Second offence: Rs 5,000.
• Third offence: Rs 10,000.
• Repeat / large-scale violations: telecom resource (sender ID, PE-ID) can be deactivated, blacklisting the brand from sending bulk SMS.

Best Practices

• Categorise messages correctly. Wrong category = scrubbing or DND violation. OTPs are service-implicit / transactional; never promotional.
• Capture explicit consent. For service-explicit SMS, store opt-in date, source, and IP address.
• Honour opt-out requests promptly. Process within 7 working days max.
• Use a managed provider. Most modern OTP APIs in India handle DND classification automatically. With StartMessaging you do not have to touch any of it for OTP traffic.

FAQ

DND is mostly invisible to OTP-focused products because OTP traffic is exempt. If you also send promotional SMS, build a clean consent-management workflow up front; retrofitting it under regulator pressure is expensive.