Beginning with GP 2015R2, you now have the ability to mask your employee’s Social Security Number on specific payroll reports.
To do this, access the Report Masking Window (GP > Tools > Setup > Payroll > Payroll). This will bring up the Payroll Setup window. From this window, select the SSN Mask button.

A window will pop up that will list all the reports that have the option of masking the employee social security number. You can select each report as needed, or none of them.

It is important to note that the format of the SSN mask will be XXX-XX-XXXX and is not user editable. Users can’t select which digits would be masked, it is either all or none.