Check type of tax procedure

Hello experts,

Please let me know how to:

1. Check which tax procedure is implemented in TAXINN or TAXINJ (with SPRO path)    - ECC 6.0

2. If TAXINN, how to maintain the effective %age of condition (for eg JMOP) as 15% from 12% to make the system calculate the JMOP as 15% from "X" date and keep on calculating 12% for posting date before that "X" date.

thanks