Had lots of dealings with HMRC over the years (single mum, 3 DCs, many tax credit claims and HMRC shenanigans, so I pretty much know the answer to my title question!)
I'll try and keep this as short as possible...
I had a TC overpayment demand from HMRC (all caused by their mistake, which I repeatedly told them about). The debt went to a debt collection agency. I phoned the DCA as soon as I got the letter and said I couldn't make any repayments as I was in financial difficulties due to my TC being stopped. They were great and said they'd refer the debt back to HMRC and I would hear from them in about 6 months time.
That was back in February, so it's now been 10 months.
In my fantasy world HMRC have looked into my case, realised what a massive cock up they have made and have quietly chucked my file into the bin.
Back in the real world I know that I could be a little old lady sat in my rocking chair in 30 years time and a HMRC letter will plop onto my doormat demanding the overpayment back.
Has anyone ever had a TC overpayment demand from the HMRC 'forgotten' about?