ARIBA DSN - Supplier invoice - Allowance % net / gross

Hi all,

We realized than allowance % is calculated over amount without taxes. Is there any option to be calculated over amount with taxes?

Our customer has this scheme (allowances marked in bold):

Amount DH/HTVA : XXXX

VAT 20% : YYYY

Amount DH/TTC : ZZZZ

Advanced payment amortization if any : ZZZZ*10% -> ALLOWANCE over amount + taxes

Retention of warranty 10% if any : ZZZZ*10% -> ALLOWANCE over amount + taxes

Net to be paid : WWW

Thanks.