Exchange Rate Difference generated when process payment w/ withholding tax

Question

I post a foreign currency vendor invoice w/ withholding tax posting
that is related to the expense transaction. We have assigned a
withholding tax type '01' for invoice posting (that means the
withholding tax calculated during invoice posting). And this
withholding tax amount is calculated using special exchange rate
announced by Bank of Thailand (BOT). And this posting is fine. e.g. Dr
Expense Cr Vendor Cr Withholding tax.. The withholding tax amount is
calculated based on BOT rate, Expense posting is based on M rate and
the AP posting is equal to Expense Posting minus withholding tax
posting..
Assume BOT Rate is 3:1 and M rate is 2:1
FC LC
Dr Expense 100 200
Cr Vendor 85 155
Cr WH Tax 15 45
When I process outgoing payment with foreign currency for this invoice,
system always take M rate (or I use special document type to force the
system use BOT rate), but either these two results will make the
posting imbalance in Local currency, then make posting to exchange
gain/loss..
How can this problem solved? Any configuration control? Or what we only
can do is to input the LC amount during payment posting..
Please advice.
Angus

Answer 1

Please check table V_T7XSSPERSUBTYP, where in the subtypes for specific countries / cities need to be maintained for different infotypes. In this case check for IT0210.
If helps, pl do reward.