Thank you. The way estoppel operates is that if the following conditions are satisfied, then an employee should be able to use it as a defence to resist the recovery of an earlier overpayment:
· The overpayments were made due to an error by the employer
· The employee genuinely believed they were entitled to the money, or did not even realise that they were being overpaid
· The employee has since 'changed their position', meaning they have spent the money in question. However, this does not mean just spending it on usual items of expenditure, such as bills, everyday spending, etc – you must have gone out of your way and changed your position, such as making additional purchases which you would not have done had you not received that money.
I am not sure you would satisfy this because you have not changed your position, you merely transferred the money to savings. So overall I the employer was to pursue you for this money then they are likely to succeed in recovering it. In the end, errors do happen, as long as humans are involved in something there will be errors. You have not been greatly inconvenienced in the grand scheme of things here – you were paid money that was not yours, you quickly transferred it over to a different account and now are being asked to return it. The right (and legal) thing to do is return it and unless you have suffered any actual losses (not inconvenience as that is not compensated) , then you cannot ask for any compensation either