Define Welfare Fund Contribution Value 
Procedure
If the employee chooses a Welfare fund different to that of the company, the contribution value for this plan must be entered manually using a wage type in the Recurring payments/deductions infotype (0014).
Result
The system calculates by default the difference between the Welfare fund contributions that correspond to the company plan and those that the employee makes to a specified Welfare fund plan of their own choice. This difference is stored in a wage type that you use as an employee deduction. That is, the employee is responsible for this difference.
If the company policy differs from the above, you can change this standard setting using a user exit.
To do this, see the Implementation G uide, in section Payroll ® Customer Modifications Processing ® Procedures ® Maintain Calculation of Difference Between Welfare Fund Contribution and Plan.