---
title: Why was my DLT header deactivated, and how many variables can a template have?
description: "TRAI's February 2025 amendment added rules on inactive headers and on how templates are built. Both can cause failures that look puzzling at first. ## Headers unused for 90 days are deactivated If a header (sender ID) sends **no messages…"
url: "https://www.smsgatewaycenter.com/blog/kb/why-was-my-dlt-header-deactivated-and-how-many-variables-can-a-template-have/"
updated: "2026-09-18"
category: Bulk SMS / DLT
---

# Why was my DLT header deactivated, and how many variables can a template have?

TRAI's February 2025 amendment added rules on inactive headers and on how templates are built. Both can cause failures that look puzzling at first.

## Headers unused for 90 days are deactivated

If a header (sender ID) sends **no messages for 90 days**, it is deactivated automatically. Messages sent with it afterwards fail as an invalid or blocked sender.

- **To reactivate:** log in to your DLT portal and request reactivation of the header.
- **To prevent it:** review your headers every quarter. Retire the ones you no longer need and keep the rest in use.

## Limits on template variables

- A template can normally have **up to three variables**. More are allowed only in special cases, with justification to the operator.
- At least **30% of the template** must be fixed text. A template made almost entirely of variables will be rejected.
- Each variable must use the correct tag, such as `{#numeric#}` or `{#url#}`. See *What are DLT variable tags, and which one should I use?*

## One template, one header

A content template cannot be linked to more than one header. If you send the same text from two headers, register it once per header. Otherwise the message fails with a sender ID mismatch (**SENDERID_MISMATCH**).

## Quick checklist before registering a template

- The right category (see *Which category should I register my DLT template under?*)
- Mostly fixed text, with no more variables than you need
- Every link and callback number whitelisted
- Linked to the single header that will send it

**Official source:** [TCCCPR (Second Amendment) Regulations, 12 Feb 2025](https://www.trai.gov.in/sites/default/files/2025-02/Regulation_12022025.pdf).

### More Related Articles

- [What is DLT digital consent, and do I need to act on it now?](https://www.smsgatewaycenter.com/blog/kb/what-is-dlt-digital-consent-and-do-i-need-to-act-on-it-now/)
- [What is the PE-TM chain, and why do messages fail without it?](https://www.smsgatewaycenter.com/blog/kb/what-is-the-pe-tm-chain-and-why-do-messages-fail-without-it/)
- [Which category should I register my DLT template under?](https://www.smsgatewaycenter.com/blog/kb/which-category-should-i-register-my-dlt-template-under/)

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