try links
How to Implement a BAdI - Enhancement Framework - SAP Library
Badi Implementation Step by Step Needed. | SCN
https://www.consolut.com/en/s/sap-ides-access/d/s/doc/YY-PAY_IN_LON_604
CL_IM_HR_IN_LN_REPAY_PLAN SAP ABAP Class - Imp. class for BAdI imp. HR_IN_LN_REPAYMENTPL
https://apps.support.sap.com/sap/support/knowledge/preview/en/2194527
Loans Enhancement - India - Payroll India (PY-IN) - SAP Library
https://hrnetwork.files.wordpress.com/2010/02/payroll-india-documentation.doc