MIRO - reference number

Hi,

When I write a letter 'A' or 'A0001'(document type 'CG': accounting banking expenses) in the reference field, the system gives me the following error:

"Letter of indicated Reference and Branch N° is incorrect."

"The document class CG demands the Letter of Reference and Branch N°"

Do you know where I can find the customizing of these attributes?

In Argentina, for example A=type of document (bill, credit note, etc) ; 0001=branch number

At the end, the system should assign the correct number, which is internally calculated.

Thanks for your help.

Liliana.