TRAI SMS Rules 2025: What Do 'S', 'P', 'G', and 'T' in message headers really mean?

Have you ever paid attention to the letters at the end of an SMS sender ID—like S, P, G, or T? If not, it's time you do. The Telecom Regulatory Authority of India (TRAI) has implemented an SMS Suffix System for 2025 that makes these alphabets more than just letters — they’re key indicators of the type of message you're receiving.

With over 1.1 billion mobile users in the country often bombarded by spam and scam messages, TRAI’s move aims to simplify SMS identification and enhance consumer safety.

What do the letters mean?

TRAI mandates that every SMS header must now end with a specific letter that categorizes the message type:

• P – Promotional Message (e.g., advertisements, discounts, product offers)
• S – Service Message (e.g., updates, reminders, informational alerts)
• T – Transactional Message (e.g., OTPs, bank alerts, purchase confirmations)
• G – Government-authorized Message (e.g., official government communication)

For instance, if you receive a promotional message from Airtel in Delhi, its sender ID will read something like AD-Airtel-P. If it’s a transactional alert from Axis Bank, it might be AX-Axis-T.

Why this matters

This classification allows users to identify the nature of the SMS at a glance—without opening the message. It helps in:

• Filtering spam and scams more efficiently
• Prioritising important notifications like OTPs or government updates
• Avoiding fraudulent schemes masked as official communication

Given the rising number of scam messages circulating in India, this simple system can significantly reduce the risk of users falling victim to phishing or fraud.

So next time an SMS pops up on your phone, don’t ignore the last letter of the sender ID. S, P, G, or T—these small indicators carry big meaning. Understanding them could help you separate the useful from the useless—and potentially protect you from costly scams.