When you send a document to a registered user system using a special code, it is assumed that you sent it. This special code is called a unique user identifier and it is like a secret password that only you know. If someone else uses your code, you can prove it was not you who sent the document.

If you tell Customs that your special code is no longer secure, then the rule that assumes you sent the document does not apply. You can tell Customs that your code is not secure if someone else has found it out. This means that you will not be blamed for sending a document if someone else used your code.

You can look at the Customs and Excise Act 1986 to compare the rules. This act has similar rules about unique user identifiers. It helps to understand how the rules work and what you need to do to keep your code secure.