budget change effect in tax codes

Dear All,

Due to the budget change recently, the tax code values have also changed. Now we still have some PO's, GR.MIRO pending. My question is after the change takes place / with effect..what necessary changes do i have to make. Here some 50 tax codes are used. Do i have to create once more the new tax codes? I tried changing the % value of bed from 10 to 12. i.e: With the existing one i made a new entriy as 12 % also in fv11 and gave the starting date as todays. Now when i went and made a PO with back date the values for bed(10%) came for the previous date and when i made a PO for todays date the value 12 % came.

But in MIGO amd MIRO the bed calculated is 12% for both the cases. Please note that i have also changed the posting and doc date to previous date for one cycle run and in the other i kept todays date. Yet there was no change.

In FV11 the condition record is based on tax code.

Pl suggest. Am i missing something.