1242 - Your client reference
This is a reference that you assign to your individual client when requesting
to be authorised as their agent. For Self Assessment, Corporation Tax and VAT
you may enter a maximum of 20 characters. For PAYE the maximum is 16
characters. We recommend that you don't use client credentials such as the
Unique Taxpayer Reference (UTR).
You can add or change your client reference using the 'Manage Client' service.