stamp taxes

Dear Community,

In Tunisia, there is a legal requirement to have a 0.3 TND stamp fees (taxes) added on every sales invoice, and computed on the total amount. This tax is a fixed amount.

I have entered a new conditions type (TIMB) in taxes conditions procedure . I have also entered a new condition type in the pricing procedure.These two conditions types have the same Accés key (TMB).

In the calculating, i defined tax code for sales and purchase.(A8)

In the posting (OB40), i defined a tax account for A8

in the transaction VFX3, this message appear:

Error in determination account T030K PSTQ TMB

I am stuck here and I would appreciate any kind of help or if someone can direct me to the correct way on investigation.

Thanks in advance,

Meher