Budget is not getting checked for tax Amount in PO

    Hi user i am trying to Create Purchase order Budget is checked at the PO value that is ok,

But when i am including tax in the PO at that time  Budget is not checked fot tax amount.

For EX i have created  a PO of 10000 rs and tax 120 rs

budget is checked for only 1000 rs 120 go without budget check.

Please provide any solution .

Regards

Sandeep