DWP keep sending letters to my address about someone else's UC overpayments

Hi there,

Not sure if this is within the scope of the forum, but here goes.

I keep receiving documents in the post, coded UCD694, from UC about 'cost of living overpayments' on behalf of another person who doesn't - and to my knowledge has never - lived at my address. I've lived here for 20 years, and I'm equally certain that the previous occupier isn't this person, either. Not sure if it's an admin error by UC, or if Mr X is working some kind of fraudulent claim. I've 'returned to sender' marked 'not at this address' at least half a dozen times now, but the letters just keep coming. Today letter number 7 arrived, and so finally I opened it to try to find out exactly what is going on.

The letter concerns an overpayment of £300+ to Mr X, which they say they'll be withdrawing automatically from *his* monthly payments, so on the face of it, besides being an annoyance this probably shouldn't affect me directly, should it?

However - I am going to have to migrate to UC from ESA at some point in the future, and now I'm wondering if this situation, which is not of my making, might have any kind of detrimental effect on that transition?

The UC 'help'line was of course anything but, with them basically saying 'not our problem, mate' (!). And because I'm not Mr X they won't even discuss it with me, even though I can easily prove that I am the real occupier of the address. The whole thing looks a bit 'off' though anyway, there's no reference number or anything on the letter (which I might add was a *great* help during the phone call).

What can I do to clear this up before I get my 'invitation' to migrate? Do I even need to worry about it?

Any advice gratefully received, as always.