At ICS Legal, I identified an income tax withholding error where an employee's tax code was incorrectly set, over-withholding £500 monthly. I reviewed payroll via Xero, confirmed the error with HMRC's tax code update, and adjusted the code in our system. We issued a refund and amended P60 forms, ensuring compliance. The employee was satisfied, and no penalties were incurred. I learned to conduct monthly payroll audits and cross-check tax codes with HMRC notices, reducing errors by 25%. Tip: Regularly audit payroll against HMRC updates to catch withholding errors early.