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Check Digit Tool

All containers used for international shipping, including tank containers, must have a unique registration number. This unique number is made up of the following elements :-

  • Four letter prefix. The first three of which designate the owner, the fourth is always ‘U’ identifying the unit as a container; this is known as a BIC code. see

    For example CLLU – Cassilon Liquid Logistics unit
  • Six digit suffix. This complete number is designated by the owner, contrived to own requirements.
  • A single check digit added at the end.

The check digit is there to pick up any errors which might be caused by incorrect transcription of the registration number. It does not matter where in the world you are, if you have a wrong check digit you have an invalid container number – and an invalid container number is impossible to trace through the seafreight shipping process.

Check Digit example

Please try our check digit calculator below. Your number should comprise 4 alpha and 6 numeric, no spaces or punctuation.

Please input Container Number:


Cassilon Limited
Registered in England & Wales
Company registration number 7222500
VAT registration number GB 676 9879 42

Telephone +44 1206 299002    Fax +44 1206 299337


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