I don't know if this is feasible for you or not, but I always edit the original pay cheque to contain all of the correct information for that payroll.  Then I create an 'Advance' item, either + or -, whichever way it works out, for the difference in the net pay that the adjustment creates.  The net pay cannot change on that cheque, as it has already been issued.  But if you put the net pay difference to an 'Advance', then on the next payroll, you simply reverse whatever 'Advance' you created on the first pay cheque.  Of course, the employee should receive a revised paystub explaining what took place.