DLT registration: why a clinic's SMS needs it The TRAI 2018 regulations behind the sender, header and template steps, and which messages they catch.

DLT registration is the process by which a business that sends commercial SMS in India registers itself as a sender, its headers and its content templates on a telecom operator's Distributed Ledger Technology platform under TRAI's Telecom Commercial Communications Customer Preference Regulations, 2018 (6 of 2018, 19 July 2018), so that the operator's checks let its messages through. Regulation 13 says access providers "shall adopt Distributed Ledger Technology (DLT) with permissioned and private DLT networks" to "ensure that all necessary regulatory pre-checks are carried out for sending Commercial Communication". The SMS gateways that clinics buy from sit on top of those networks.

What does a sender register?

1. The entity. Access providers must "Register Sender(s) and assign the header(s), header root(s)" through an Entity Register, "a Distributed Ledger for Entities (DL-Entities) having a records of all entities registered to carry out telemarketing related function(s)". The gateway calls this the principal entity, and the 2025 amendment uses the same term.
2. The header. Defined as "an alphanumeric string of maximum eleven characters or numbers assigned to an individual, business or legal entity under these regulations to send commercial communications". Every access provider must ensure commercial communication on its network "only takes place using registered header(s) assigned to the sender(s)".
3. The content templates. The Content Template Register keeps "records of unique content template identity along with the content of content template and details of sender who got it registered". A message that does not match a registered template is blocked.
4. Consent templates, where the clinic sends promotional messages and needs recorded consent.

Which clinic messages does this catch?

The regulation defines a commercial communication as any message "where the primary purpose is to inform about or advertise or solicit business for" goods, services or a supplier. It then splits messages into kinds. A "Transactional message" is one "triggered by a transaction performed by the Subscriber ... sent within thirty minutes of the transaction being performed and is directly related to it", with OTPs as the example. A "Service message" is sent "either with his consent or using a template registered for the purpose" to facilitate, complete or confirm a transaction the recipient entered into. "Promotional messages" are those "for which the sender has not taken any explicit consent from the intended Recipient", and regulation 9 bars any commercial communication that does not match the recipient's registered preferences or consent. A token or appointment confirmation sits in the service bucket; a camp announcement or a discount offer is promotional and needs consent on record, and the NMC's advertising rules apply on top; see WhatsApp and SMS for clinics.

What changed in 2025?

The Second Amendment Regulations, 2025 (1 of 2025, 12 February 2025) tightened the ledger. Headers and content templates not used for ninety days are to be temporarily deactivated and reactivated on request. A content template may carry more than three variables only "in special circumstances and on requisition with reasons and proper justification from Principal Entity". Consent-seeking messages go out on a dedicated short code (127xxx) that names the principal entity. A clinic that registered a header years ago and let it sit may find it switched off.

What does this look like for a small OPD?

A clinic that wants to send its own appointment reminders through an SMS gateway registers once as a sender on one operator's DLT portal, picks a header, and submits each message wording as a template with variables for the patient's name, date and time. Reminders then go out only in that wording; each new wording is a new template. Our post on reducing no-shows covers what to put in the message.