How to retroactively add vacation pay?

SOLVED

There are a couple of employees who should have had 6% vacation pay and they were receiving 4%. All of our employees bank their vacation pay and receive a pay out in December.

I've gone back and figured out how much they are owed, and I'm ready to put it into Sage so that their December pay out will be correct.

However, when I try to put in a payroll cheque for just vacation pay and bank it, I end up with a cheque that has a negative amount.

Sage is set up so that the vacation pay has deductions taken before it is banked, but we have been banking the pre-deduction amount.

I realize that if I don't take off deductions, not only can it affect their Income Tax, but it will also affect our Payroll Deductions. If I bank the post-deduction amount, that's not the amount the employee would have had if they had been banking the 6% all year.

What is the best way to adjust the vacation pay that is banked?