Tax in AP (invoice)

Dear all,

i have an issue when created invoice,

i have invoice with two lines on detail. both line are charged with tax which is Tax and Witholding.

system setup :

Tax = 10%

Witholding = 2%

--------------------------------

we describe with amount below :

Item            =  2,700,000

Witholding   =      59,400

Subtotal      =  2,640,600

Tax             =     270,000

Total           =  2,910,600

which is supposed :

Item            =  2,700,000

Witholding   =      54,000

Subtotal      =  2,646,000

Tax             =     270,000

Total           =  2,916,000

it seems like amount in Witholding are :

(Item + Tax)* Witholding

which is supposed

Item * Witholding

i try to reproduce in my server test but its normal, no issue, the result is that supposed.

can anybody explain how could that happen?

Regards,

Suryadi