What Is USSD? How *323# Codes Work and the ₦6.98 Bank Fee

USSD (Unstructured Supplementary Service Data) is the menu service you reach when you dial a short code that starts with * and ends with #, like *323# or *310#. It opens a live, two-way session between your phone and your network or bank, and it works on any phone with signal, no data needed.

That's the short answer to what is USSD. Balance checks are free. A bank transfer by code costs ₦6.98 a session, taken from your airtime.

What is USSD doing when you dial *323#?

Press call and your code rides the signalling channel your phone already uses to set up calls. A gateway reads it. Within seconds a menu comes back, and each number you reply with loads the next screen until the session ends. Leave it idle and it closes, which is exactly how you get cut off halfway through typing an account number.

Networks run self-service codes such as *310# for airtime and *323# for data, part of the short codes the NCC harmonised across every network. Banks run their own, like GTBank's *737#, but those menus still pass through your network. So a small button phone handles them fine.

Worked example: a free *323# balance check, then a ₦6.98 *737# transfer

Say you check your MTN data, then send ₦5,000 to your sister.

1. Dial *323# on your MTN line. Your data balance shows, with no bank fee.
2. Dial *737# to open GTBank's transfer menu.
3. Accept the prompt for the ₦6.98 session fee.
4. Enter the amount and pick your sister's account.
5. Type your PIN.

The money leaves your bank account. The fee leaves your airtime. If the menu times out before you reach the PIN, go back to step 2.

How much does dialling a code cost? Free network codes vs the ₦6.98 bank fee

Dialling *310# or *323# costs nothing, and a bundle bought by code costs only the bundle price.

Bank sessions are different. The CBN and NCC first set the fee in March 2021 as a flat charge on your bank account. Since 3 June 2025 the NCC has moved it to airtime. Your network takes it for sessions of up to 120 seconds, and only after you accept the prompt. That rule still stands as at 24 October 2026.

Codes, texts and apps: which needs data and which keeps a record

Most people asking what is USSD really want to know how it compares with a text or an app.

No USSD reply lands in your inbox, so screenshot the confirmation before you close it.

Seeing "Invalid MMI code"? It isn't a fee or a ban. Check the * and the #, look at your signal bars, and on a dual-SIM phone switch to the line that holds airtime before you try again a minute later.

Keeping your PIN and calls safe

Type your PIN only into the prompt on your own phone. No bank, network or AidaPay staff will ever ask for it. If a caller does, hang up and ring the number printed on your card.

Watch for the reward scam. A stranger promises a prize and gives you a code to dial, and that code switches on call forwarding, so your bank's calls and one-time passwords (OTPs) ring on the scammer's phone. Never dial a code from someone you don't know. Dial ##002# to cancel all forwarding.

Lost your SIM? Call your bank at once and block USSD banking on that number. When you just need credit, you can buy airtime online without dialling a code.

Related terms

See the data balance codes for every network, the full list of MTN USSD codes, and the entries for VTU, SME data and airtime to cash. Every other term sits in the full AidaPay glossary.

Frequently asked questions

Published 24 October 2026. Prices and codes change - if you spot one that has moved, tell us and we will fix it.