IHTM02142 - Communications: British Document Exchange: when to use British Document Exchange
Where you receive correspondence which indicates that a solicitor or accountant is a member of British Document Exchange (DX) (IHTM02141) you should address any communication, including assessments, using the DX number and exchange.
You do not need to write the postcode on DX correspondence.
DX ‘numbers’ of firms in Scotland and Northern Ireland may consist of numbers with letters before or after them. Where this is the case you should include the letters in the DX address.
Where a repayment is to be addressed to a member of the DX system, you should also make sure the DX number and exchange is entered in the address box on form Sect 6.
If you are in any doubt about the correct form of address, you should check it with the DX Directory (IHTM02147).