Advance payment include tax amount also in ME2DP

Hi Team,

i am trying to post advance payment request & Payment through ME2DP,

but system is calculating Advance payment amount on base value.

suppose 1 Material with 10000/- taxes VAT (5%) total PO value is 10500.

whenever i am entering down payment in PO, it is calculating on 10000.

how to solve this

regards

Sri