UK Guidance: AEIM 102080: The account number to be reported is the unique identifying number or code that the reporting financial institution has assigned to the Reportable Account. This will include identifiers such as bank account numbers and policy numbers for insurance contracts as well as other non-traditional unique identifiers. The unique identifier should be sufficient to enable the financial institution to identify the Reportable Account in future. Where there is not a unique identifying number or code the financial institution should report any functional equivalent that they use to identify the account. This may include non-unique identifiers that relate to a class of interests, which, along with the name of the Account Holder, enable the account to be identified. Exceptionally, if the Reportable Account does not have any form of identifying number or code the financial institution should report a description of the account sufficient to identify the account held by the named Account Holder in future.