WHT at Payment Behavior

Summary:

We used WHT calculation generated at payment time.

Based on what we test, the WHT always deducted at the first payment in case of partial payment.

Content (required):

For example :

Invoice amount 10,000, WHT : 2 %

1st payment : payment amount 2,000 and WHT deducted 2% (20)

2nd payment : payment amount 8,000 and no WHT deduction.

Is this the standard behavior? is it possible to have prorate WHT deduction based on payment amount?

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):