DND and the NCPR explained: what scrubbing really means

DND is the preference register that TRAI makes telecom operators keep. A customer uses it to say which kinds of commercial communication they will not accept, and when: by dialling or texting 1909, or through the TRAI DND app. It is still widely called the NCPR, the National Customer Preference Register. Before a promotional call goes out, the calling list has to be scrubbed against it through the DLT system, which only a registered sender or telemarketer can reach. A calling vendor's own suppression list is a different thing. BlackWolf checks its list before every dial, but scrubbing against the national register needs the client's DLT access.

What the NCPR is

Under the TCCCPR, TRAI's 2018 regulations, the register is a distributed ledger for preferences, kept by the operators on DLT. The regulations call it the Preference Register. TRAI's own FAQ on unsolicited commercial communication calls it the "National Customer Preference Register (NCPR) also known as DND Registry", and so does nearly everyone else. In this post, DND and NCPR mean the same register.

It is large, and it is not universal. TRAI's quarterly report of 4 August 2026 (PDF), opens in a new tab counts 224 million registered preferences at 30 June 2026, about 16% of 1.348 billion subscribers. TRAI adds that the rest, more than 1.12 billion subscribers, have registered no preference and are reachable by registered senders. Nobody should read that as permission to call anyone. It does mean the register is a filter on who may receive promotional calls, not a list of everyone who dislikes them.

What a customer can block

Preferences have four parts, set out in Schedule-II of the 2018 regulations (PDF), opens in a new tab and TRAI's preference registration page.

Category. As of September 2026:

A customer can send "BLOCK 2" to 1909 and stop property promotions while still hearing from their bank. There was also a "fully block" option. The Third Amendment of 18 September 2026 (PDF), opens in a new tab folds it into the promotional block, migrating existing registrations within fifteen days of the amendment coming into force.

Mode. Voice call, SMS, auto-dialler calls with a recorded announcement, auto-dialler calls connected to a live agent, and robo calls. How an AI agent's call is classed by mode is a question to settle with your telemarketer and operator, not to guess.

Time band. Nine bands across the day, four of them off by default. We cover them in calling hours for commercial calls in India.

Day type. Each day of the week, plus public and national holidays.

Operators must acknowledge a registration within fifteen minutes and give effect to it within 24 hours. A block on promotional communication does not stop service or transactional communication.

Consent can override a preference

A preference is a default. Consent is a specific permission, and it wins.

Under the Second Amendment of 12 February 2025 (PDF), opens in a new tab, a promotional call may be delivered to a customer who has not blocked that category, or who has given consent. Explicit consent acquired digitally lets a sender's promotional calls reach that customer whatever their registered preferences. The consent-seeking message goes out from a 127-series short code, names the brand, and the confirmation tells the customer how to revoke. After a revocation, the sender may ask again only after 90 days.

Inferred consent rests on the relationship between customer and sender. The Third Amendment, once in force, defines that relationship more tightly: an enquiry the customer made in writing or by digital means counts only within the seven days before the communication, and the sender must keep the enquiry in verifiable form. A portal enquiry from last month no longer qualifies under that clause.

How scrubbing works through DLT

The regulations define scrubbing as comparing the sender's target list against the preference and consent ledgers, to check whether each number may receive the communication. The check covers the content category, consents, time bands and day types. It is done by a scrubbing function inside the DLT system, which is required to protect the register by using virtual identities instead of exposing real numbers. The output is a scrubbed list, and only that list goes to delivery.

For voice, TRAI says calls from the 140 promotional series are checked against the customer's preferences before delivery. That check belongs to a registered sender, a registered telemarketer and the operator. A vendor outside that chain has no route we know of to run the register against your leads, and it should not claim to.

In practice, a developer running a promotional campaign needs:

1. Registration as a principal entity on an operator's DLT platform.
2. A registered telemarketer linked to it, placing the calls from 140-series numbers.
3. The target list scrubbed through DLT before the campaign, not once a year.
4. Registered consents, where the campaign relies on them.

Common cases in a property pipeline

The same register lands differently depending on where a lead came from.

• A buyer who filled in a Meta or portal form this week. The enquiry clause is built for this. Call quickly, and keep the enquiry itself: the form, the timestamp, the project. We cover the mechanics of those sources in portal and Meta leads.
• A list from a launch two years ago. Nobody on it enquired in the last seven days. Every number needs scrubbing before a promotional call, and registered consent wherever you rely on consent.
• Leads from a channel partner. Ask whose enquiry it was. The relationship the regulations describe is between the customer and the sender, and the buyer may have spoken only to the partner. See channel partner leads.
• A buyer who says "main DND par hoon" (I am on DND) halfway through a call. Treat it as an instruction, not trivia. Whether or not the registration exists, the person has told you to stop.

Why a vendor's suppression list is not the same thing

Both are lists of numbers not to call. They are built from different facts, and they fail in different ways.

The last row is the point. Each list catches people the other cannot see. A compliant campaign uses both.

What BlackWolf's list does

Every number is checked against the suppression list before it is dialled, and a listed number is never rung. The list holds opt-outs heard on calls, complaints, and any number the client adds.

The opt-out is detected on the caller's own turn, in set phrasings in English, Hindi and Gujarati, and written to the list the moment it is said, automatically. "Dobara call mat karna" (don't call again), "મારો નંબર કાઢી નાખો" (maaro number kaadhi naakho: remove my number) and "Remove my number" all suppress. So does "I am on DND", because a caller who says it expects it to settle the matter, whether or not they have actually registered. "DND ka matlab kya hota hai?" (what does DND mean?) does not: asking what DND means is not asking to be put on it.

Ordinary objections are not opt-outs. "Not interested", "abhi nahi" (not now) and "my wife will decide" leave the lead where it was. Both directions are tested, in Gujarati, Hindi and English, because suppressing a live lead on a misheard phrase quietly deletes a client's pipeline.

What it cannot do

It cannot see the national register. If a buyer blocked category 2 through 1909 last year and has never spoken to you, nothing on BlackWolf's list says so. That check happens through your DLT access, and it is yours to run. Our compliance page lists what the platform enforces and what stays with you, and the full split is in the pillar guide to TRAI's TCCCPR and AI calling.

Complaints: where DND changes the outcome

Registration matters most when something goes wrong. Under the 2025 amendment, a customer can complain within seven days of an unwanted commercial call. To complain against a registered sender or telemarketer, the customer must have registered preferences. Against an unregistered sender, there is no such condition, which is one more reason never to call from an unregistered line.

A complaint names a number and a date. The fastest answer to it is the call itself: the recording, the transcript, the consent basis and the opt-out state, all against the lead. For how this works on property enquiries, see real estate.

What to do next

Ask your telemarketer when your calling list was last scrubbed through DLT, and ask your calling vendor to show you its suppression list and how an opt-out reaches it. You need both answers.

This article is general information, not legal advice.