Tax and overpayment of wages

I am seeking to repay an overpayment of wages with my employer. The issue I am seeking advice on is the actual amount I need to repay. I understand it is the net amount I actually received and that my employer needs to inform HMRC in respect of tax. My employer says I need to repay the gross amount and deal with tax myself even though I am on payroll.

Hi RPG1963,
If the repayment relates to previous years, it will be the gross amount for your employer to then submit revised end of year details once the full tax year has been repaid back.
Thank you.