I have been doing payroll weekly, I have just found out that my client has paid extra wages in cash, how do I account for this in payroll so the P60 at YE is correct?

Hi qbo18, if the payment relates to undeclared income then it would be advised to rollback the payroll and enter these onto the period in which there were paid - this will then update the pay slip and any tax deductions accordingly. The payroll can be resubmitted from QB to HMRC as a correction to an earlier submission, which will overwrite any RTI previously submitted for the period.