Overpaid by my employer

Hello. Could you advise me, please, if my employer overpays me (because of their mistake(s)) and I pay money back to my employer (if more than £10k) (without interest), should it be considered like a loan (a beneficial loan?) (for the time period when overpaid money are being held by me) for which the interest difference is taxable?

Hi
It would not be considered a beneficial loan.