HMRC are a weird org. I had to pay extra tax last year at the end of the year. They sent me a letter to tell me this, probably 6 or 7 times within 2 weeks.
I paid on receipt of the first letter.
I then got a letter to say it's been paid, again, probably 5 or 6 times, each in a different format.
I then get a letter saying it's not paid. I phone up, they apologise and say they'll send a letter to confirm it's paid. They do, another 3 times.
I mean, seriously? I've got them all - what a massive waste of taxpayer money