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Are you referring to Construction Industry Scheme (CIS) taxes, and in turn CIS Withheld Taxes, or if not CIS, can you please expand a bit on what you're looking to do.
It might be worthwhile giving our support teams a call - Have you identified which payslip they overpaid on, or has it been a cumulative over-payment over a series of months?
Our Desktop support team, who I've liaised with, feel they would be best placed to go through the payslips with you for that employee, identify what caused the over-payment, and they'll then be able to advise the best way to resolve this.
If you're confident of what caused it, and you feel you can resolve it with year end liability adjustments, this link may help: