Hello
The notice pay calculation is based on the number of notice period days maintained in infotype 0016.
This would then be applied on the basis wagetype defined in V_T539J
Kindly check what are the values as maintained in Infotype 0016, infotype 0008, and customizing in V_T539J
Further please check the following :-
1. Please check the following link for information regarding Termination payments:
http://help.sap.com/erp2005_ehp_05/helpdata/en/d7/7ca4e2cd234c0a92c798091d49afbb/content.htm
2. Also please have a look at the attached SAP note: 374197 FAQ Termination Workbench
Thanks and Kind Regards
Ramana