Error in Tax calculation.

Dear all,

I have created a tax code in TAXINN in transaction FV11(Condition type JIPC) for CST 1% . When I put this tax code in PO - at Invoice Tab page at item level and when I click on details the calculation of 1% tax on BASB Rs. 100/- Comes to Rs 4.12/- instead of Rs. 1/-. How does the system calculates excess tax. ? How to configure this in the system to get correct results. The new tax code is copied from the old tax code. if I put this old tax code in the PO the result is correct .

greetings!!

Ashish Pradhan.