In India, customers register their preferences on the telecom operators' DLT system, which people still call DND. They can block all commercial messages that need explicit consent, block promotional messages, or block specific categories such as banking, real estate or education. Transactional and service messages are not blocked by those choices, and explicit consent from the customer lets a promotional message through.
By Rohit Jadhav. Last reviewed 25 October 2026. This is operational guidance, not legal advice. Rules change, so confirm the current requirements with your provider and with TRAI.
"Do Not Disturb" is the name most people use for the system that lets customers stop unwanted marketing calls and messages. Under TRAI's current regulations the formal name is the preference register, and it is wider than a simple on-off switch. This guide explains how DND SMS rules work: what a customer can block, what still gets through and what that means for your campaigns. It is part of our main guide to DLT registration in India. For help with compliant sending, Nexcomm's bulk SMS service includes scrubbing against the registry. More guides sit under Compliance & Regulations.
What is DND in India?
DND stands for Do Not Disturb. TRAI's regulations define the preference register as a distributed ledger that records each customer's choices about commercial communication: the categories they allow, the modes (SMS or call) and the time slots and types of day. Before a commercial message is delivered, the system checks the recipient against this register. That check is called DLT scrubbing.
What can a customer block?
- Fully block: all commercial communication that needs explicit consent. Messages sent under inferred consent, and government messages, still reach them.
- Block promotional messages in general.
- Block selected categories. The regulation lists categories such as banking, insurance, financial products and credit cards, real estate, education, health, consumer goods and automobiles, and communication, broadcasting, entertainment and IT. A customer can allow some and block others.
- Choose a mode, such as allowing SMS but not calls.
- Choose time slots and days when commercial communication may be delivered.
Customers register their choices by SMS to 1909, by calling 1909 or by USSD, according to the table in the regulation.
What still gets through?
- Transactional and service messages. The blocking options exclude transactional and service-type communication sent under inferred consent. See transactional vs promotional SMS.
- Government messages sent on the directions of the Central or State Government or a body established under the Constitution, through the DLT platform. They need no consent, and the register has no option to block them.
- Promotional messages to people who gave explicit digital consent. The regulation says such messages are delivered irrespective of the preferences registered. See SMS consent in India.
What does DND mean for your campaigns?
- Know your category. A promotion cannot be sent as service. The category decides whether DND applies.
- Expect part of your list to be blocked. A customer who has blocked promotions will not receive yours unless you hold consent.
- Collect consent properly, and keep the record.
- Respect time slots. A customer may have limited delivery to certain hours, and messages outside them are held or stopped.
- Honour opt-outs. Promotional messages carry an opt-out in the same message, and the regulation says that a customer who has revoked consent can be asked again only after ninety days.
- Do not try to get around it. A message that looks like service but advertises will be flagged.
What are the penalties for ignoring it?
The regulation provides for action against senders found sending unsolicited commercial communications: barring of outgoing services of all telecom resources for fifteen days for a first violation, and disconnection for one year for repeated violations. Read the TCCCPR guide for the wider framework.
A worked example (hypothetical)
A coaching institute in Lucknow has 10,000 numbers from past enquiry forms. This is an invented example. Of them, 3,000 have blocked promotions and have not given the institute consent. The institute's promotional campaign reaches the other 7,000. For the 3,000 it sends nothing promotional. It does send a service message about the date of an exam to enrolled students, who are its own customers. Then it adds a consent tick-box to its enquiry form, so that in the next cycle more numbers can receive offers.
Common mistakes about DND
- Believing DND blocks everything. Transactional and service messages are treated differently.
- Believing DND is absolute. Explicit consent allows promotions.
- Disguising promotions as service messages. It is flagged.
- Using a list with no consent record. It fails scrubbing.
- Forgetting the opt-out. Promotional messages need it.
- Asking again too soon after an opt-out. Wait the ninety days.
Frequently asked questions
What is DND for SMS in India?
It is the system in which customers register their preferences about commercial messages and calls: which categories, which modes and which times they allow. TRAI's regulations call it the preference register.
Does DND block transactional SMS?
No. The blocking options exclude transactional and service communication sent under inferred consent. OTPs and similar messages are still delivered.
Can I send promotional SMS to DND numbers?
Only to those who have given you explicit digital consent, which lets the message through irrespective of their registered preferences. Without consent, a promotional message to a blocked number is stopped.
How does a customer register for DND?
By SMS to 1909, by calling 1909 and following the prompts, or by USSD, as set out in the regulation's tables. They choose full blocking, promotional blocking or specific categories.
How do I check if a number is on DND?
Your SMS provider's scrubbing shows which numbers fail the check. Do not scrape or guess lists. The regulation requires scrubbing functions to report requests that look like lists gathered through harvesting.
Sources checked
All checked on 25 October 2026.
- TRAI, consolidated Telecom Commercial Communications Customer Preference Regulations, 2018 (preference register, categories, blocking options, consent, government messages, penalties)
If you want to review how your list and categories interact with DND, you can reach our team through the contact page.