Hi Leah,
According to your questions, I answer to you as below.
As your inform about Back Pay to Mr.Rajesh for Payroll of May, It’s effect to report of social security. It has separate to 2 reports.
1. Social Security report of May : It mustn’t have back pay for him in the report.
2. Social Security report of April : It has back pay for Mr.Rajesh only.
Reports as the pic below.
Payroll of May for Mr.Rajesh.