I started a whole thread about HMRC's 'scam' in August. I was just back from UK where my daughter phoned them. Eventually they admitted I'd been overtaxed for possibly 15 years at first blaming DWP then admitting they had assumed I was on a full state pension (ATM it's exactly double what I get now.) I was promised back tax on three years; I've had two, totalling 5000UKP. Apparently it's your job to check they are doing their job correctly. Like some above posters no documents have been sent or at least delivered to my Thai address. The YouGov website has not been in existence for all of the missing overpaid years but there's no appeal system beyond three years.