FP04 : Write off and debiting Tax accounts

Question

Dear All,
I have an issue with debiting tax account on write off.
Scenario: Invoice posted $1000 including tax of $100.  i.e $900 consumption (revenue) + $100 tax.
GL Postings:
Customer account 1000 Dr
Revenue Account   900 Cr
Sales tax                 100 Cr.
Write off( FP04  any reason codes).
System posts the Following:
Customer account 1000 Cr
Expense Account  1000 Dr
I need it to be like:
Customer account 1000 Cr
Expense Account   900 Dr
Sales tax                 100 Dr.
I've tried everything I can, but I think I'm missing something very obvious and silly.
1) Maintained posting areas:
0120 : Expense Account (No tax code specified and tried with tax code too)
0121 : Expense Account for non tax related items (same expense account)
0122 : Tax Adjustment Flag (Tested with both flag on and off)
2) Define Act Assignments ReLU to Main Transactions
Company     Division     Act Deter        Main       Acct
1000     10          01-10               0090       Expense account
1000     10          01-10               0095       Expense account
3) ISU u2013 Define Acct Assignment Relv to Transactions
Set Main receivable account (Customer account) for all combination  of 0090 and 0095. i.e. 0010 and 0020.
Company     Division     Act Deter              Main/Sub      Acct
So what am I doing wrong?
Thank you very much.
Edited by: JayUtility on Jan 31, 2012 2:53 PM

Answer 1

Thank you Ivor. Tried that too.
I'm still stuck at:
Customer (AR) Account 1000 Cr
Expense           Account 1000  Dr
The entire invoice amount is debiting against the Expense / bad debt account.
I need that only the consumption portion should debit Expense account and the Tax portion should debit the Tax account.
Customer account  1000 Cr
Expense Account    900 Dr
Sales tax                 100 Dr.
It seems like an easy enough thing. I must be missing something.