Clear customer items w. special G/L ind. A ; VAT - relating

Dear all,

I have below issue:

When I post incoming payment, clear customer item with Special G/L Ind. A, the system posts a document which have the same VAT used in the original special G/L customer item, but this VAT doesn't have to be posted in the payment even if percentage = 0.

Company is in Italy.

I would obliged any of your comments.

Rgds,

Linh