HMRC Scare Tactics?
I took on a client last year who hadn't completed tax returns for 6 years. I got a couple in for him and have the rest ready to submit as soon as he signs the paperwork and pays the rest of my bill. He has failed to do so and HMRC have estimated two of his missing years at £20,000 tax for each year - he doesn't even have a turnover that big! Scare tactics perhaps?