VAT should post based on PO date or GR date not based on MIRO posting date

Hi,

Based on posting date in Invoice(MIRO) & condition record validity period, VAT is calculated & posting on invoice posting.

Condition record for VAT condition type with tax code(T9):

01.01.2011 to 31.01.2011-------> 4%

01.02.2011 to 28.02.2011------->12%

01.03.2011 to 31.03.2011------->14.5%

PO created and GR done on February & invoive done on March and syatem calculated VAT amount perfactly based on validity period maintained in condition recod and invoice posted.

But requirement is system should post invoice VAT amount as mentioned in the PO ( based on PO date) or GR date to post during Invoice posting in MIRO

Regards,

Biju K