After changing tax code in po,At the time of MIGO VAT Not Calculating

[former_member223966]

I have created on po, there is multiple line item's.
Po doc date is 03.09.2016
Example
Line  qty netamount vat12.5% total
1      10.  2000.    250.    2250
2.     15.  3000.    
3.     20.  4000 

First line item's GRN done and vat also calculated
Now tax rate is increased to 13.5% affecteding date from 17.09.2016

In line item's 2&3 changed tax code, after that I am booking GRN.

VAT is not calculating 
Pls advice

[former_member223966]

Issue is resolved