---
title: IATA Air Waybill Check Digit (MOD-7)
description: An 11-digit air waybill number combines a 3-digit airline prefix, a 7-digit serial, and a MOD-7 check digit. Here is the weighting and a worked example.
canonical: https://stanzaapi.com/guides/iata-air-waybill-mod-7
---

[Home](/)/[Guides](/guides)/IATA Air Waybill Check Digit (MOD-7) Explained

# IATA Air Waybill Check Digit (MOD-7) Explained

An air waybill number is a three-digit airline prefix, a seven-digit serial, and a check digit computed by weighting the serial digits 8 to 2 and taking the remainder modulo 7.

Updated 2026-10-01 · 4 min read

## What an air waybill number is

An IATA air waybill number has three parts: the three-digit airline accounting prefix, a seven-digit serial number, and a single check digit.

The prefix identifies the issuing carrier and is assigned by IATA. The serial is the shipment reference within that carrier.

## The check digit

The seven serial digits are weighted from 8 down to 2 — the first digit by 8, the second by 7, and so on. The weighted products are summed and taken modulo 7; the remainder is the check digit.

For the serial 1234567 the weighted sum is 112, and 112 modulo 7 is 0, so the check digit is 0.

## The e-ticket uses the same shape

A 13-digit IATA electronic ticket number is a three-digit airline prefix plus a ten-digit ticket number, whose final digit is a MOD-7 check digit over the preceding digits.

## What it does not prove

A valid check digit means the number is well formed. It does not confirm that the shipment exists, that the prefix is still allocated, or that the goods are cleared.

## Try it on real data

[IATA Air Cargo AWB & Aviation Validator API → — Instant sub-5ms IATA Resolution 600a Air Waybill (11-digit MOD-7), Resolution 722e Electronic Ticket, Resolution 740 Baggage Tag validator, and 500+ Airline Accounting Prefix Resolver — Open the tool](/tools/iata-validator/)

## Frequently Asked Questions

How many digits is an air waybill number?

Eleven: a three-digit airline prefix, a seven-digit serial, and one check digit.

What modulus does IATA use?

Modulo 7, applied to a weighted sum of the seven serial digits weighted 8, 7, 6, 5, 4, 3, 2.

Is the check digit the same for e-tickets?

The shape differs (13 digits) but the mechanism is the same MOD-7 check digit over the preceding digits.

## Primary sources

- [IATA — Resolutions and standards](https://www.iata.org/en/publications/manuals/)
- [IATA — Air waybill (Resolution 600a)](https://www.iata.org/)