It is not possible to only show part of a Social Security Number on an employee's check stub.  However, you can remove the Social Security Number from the stub completely with the following steps:

1. Click on Payroll > Setup > Check Formats.
2. Click <C>hange and select the Payroll bank (you may press F1 to see a list of banks).
3. Click the Page Down button until field 3 appears.
4. Type 3 and press the Enter key.
5. Press the Enter key until you reach the Optional line that shows data item .T TID. This is the Social Security number.
6. Change the Column and Length settings to 0 and remove the data item .T TID from the Data Item field.
7. Continue to press the Enter key until you see "Enter Field to be changed (0 to accept)" appears at the top.
8. Type 0 and press the Enter key.
9. Press ESC and then <E>nd to close the screen. Now when you print checks the SSN will not appear on the stub.