Payment to tax authority and foreign supplier

Hi

While making the payment to Withholding tax supplier(tax Authority) I can able to make the proper payment as per the withholding tax percentage specified, but at the time of making the payment to the actual supplier, the system is not allowing/showing to make full payment, the payment I should make to the actual supplier should be $500 but instead its showing $475 in payment history. Supplier Ledger Inquiry seems ok. When I print the payment it shows $475 payment.

Kindly advise,

Thanks & Regards,

Nadir