What the tool recognises
A number is recognised by its shape, with or without spaces and hyphens:
- IMO number: 7 digits, with or without the IMO prefix. The last one is the check digit: the first six, multiplied by 7, 6, 5, 4, 3 and 2, give a sum whose units digit it repeats
- container: 3 owner letters, a category letter (U, J or Z), 6 serial digits and a check digit (ISO 6346). European swap bodies and semi-trailers carry an ILU code of the same shape, with the letter A, B, D, E or K
- air waybill (AWB): 11 digits, made of the airline's 3-digit prefix, 7 serial digits and a check digit, the remainder of the serial divided by 7
- flight: the airline's two-character IATA code, then 1 to 4 digits (AF1187). A flight has no check digit: only its format is checked
Why these numbers matter in customs
The identity of the means of transport and the container number appear in the entry summary declaration (ENS, ICS2 system) and in import and export declarations. A typo is caught here before it goes into a file.
The Customs Check file checker applies the same checks: an IMO or container number with a wrong check digit is an error on the field, a flight or air waybill with an unusual format is a warning.
What the tool does not check
A correct check digit proves that the number is well formed, not that the ship or container exists or where it is: the tool consults no register and tracks no ship. The air waybill prefix and the airline code are not compared with the IATA list. A house air waybill follows the forwarder's own numbering and has no such check digit.
Frequently asked questions
Where do I find a ship's IMO number?
On the bill of lading or the arrival notice, from the shipping line or your forwarder. It stays with the ship for life, even if its name or flag changes.
Where do I read a container number?
On the doors and sides of the container, and on the bill of lading. The last digit, often boxed, is the check digit.
Is the check free?
Yes, with no sign-up. The check runs in your browser: the number is not sent to our servers.
Is a 9-digit number an IMO number?
No. It is often the MMSI, the ship's radio identifier, which can change with its flag. Declarations ask for the 7-digit IMO number.
Is your file ready?
Check it for free in a few minutes, before you prepare your declaration.