Tax configuration TAXBRA

Hi,

My requirement is to configure tax on sales/purchases such that the accounting entries generated are:

MIGO

Dr Expense a/c - 100

Cr GR/IR a/c - 100

MIRO

Dr GR/IR a/c - 100

Dr Expense a/c - 15

Cr Tax a/c - 15

Cr Vendor a/c - 100

However with my current configuration what I'm getting is as below:

MIGO

Dr Expense a/c - 100

Cr GR/IR a/c - 100

MIRO

Dr GR/IR a/c - 85

Cr Tax a/c - 15

Cr Vendor a/c - 100

Please let me know what & where needs to be corrected?

Thanks and regards