Must I return the money

[SussexMedley]

Finished my old job, having used all my annual leave for the year. final salary should be reduced to account for the fact I've taken more leave than is proportionate for the shortened year I've worked. I submitted all forms accurately and on time. They're now saying they didn't calculate it correctly and I need to give money back. Do I have to? TIA.....

Of course you do unfortunately. There will be something in your contract to that effect.
You could always offer monthly payments?

I would ask for there calculations but ultimately yes you do

Yes but as it’s their mistake they should give you a payment plan if it’s not something you can manage in one go.

You will have no choice, it will be deducted when your final salary is paid.

That was my final salary...they're saying they messed up after paying me.

You'll need to pay them back still, presumably you'll be wanting a reference, and to avoid legal action against you.
As pp said though, check their maths.

Ask them whether they would waive it as it was their error

Yes. I act for clients who sue ex employees for not returning such payments. Sorry. Not saying they will sue you, but legally you're not entitled to the money, even though it's their mistake. It's called unjust enrichment.

Dang it. Ok, thank you all. They're a very rich company.

Of course you do - if they had made a mistake and underpaid you, you'd expect them to rectify that, wouldn't you!

Sorry, x post. But the wealth of the company doesn't come into it.

Tbh I work in HR and times when we've overpaid people we never actually have sued them to get it back. Sometimes we've agreed they can keep it if it's a small. Amount and our error.
How. Much are we talking about?

I know the wealth of the company wouldn't make a difference legally, but I just wanted it clear that I'm not thinking of how much I can get off some small, independent business. Also I wondered if it was more likely that they'd write it off, given how many bajillions they've got (and how much they waste, but that's another story).

Not talking a huge amount, a few hundred.

I would ask them to consider waiving it as a goodwill gesture considering it was their error.

Some employers would waive it, but this one is obviously not going to, which is perfectly acceptable.

How long ago was this exactly? Just wondering about the payment plan mentioned by another poster above. If you received an overpayment of “a few hundred” a couple of weeks ago, a payment plan shouldn’t be necessary. It’s not like one of those situations where someone receives more pay than they’re supposed to over a period of time, has genuine reason to believe it was theirs and therefore a payment plan to give it back is appropriate. Single overpayments discovered quickly ought to be immediately repayable, particularly if it’s such a large amount all in one go, therefore not reasonable to think it was correct.