Tax code should take according to PO

Dear Experts,

we are working as end user not as a consultant ,we don't have authorization to contact directly to our consultant too.

while booking the IR in MIRO we have to select the tax code according to invoice copy.manually we have to update the tax code which is time consuming .kindly can any one help us where according to PO system should take the tax code automatically please help us we are facing problem regarding this .

thanks