HMRC wants to tax you twice – Don’t let them get away with it.
I just saved client a few hundred pounds. After filing a tax return for 2017/18, HMRC decide to apply what they call an In Year Adjustment (a new system I was told), Here they take any income they can tax through the code system and apply a charge to tax on such income, even thought the year is long past and any chance to change a PAYE code has long gone. So although the client was paying tax on property income via self-assessment, HMRC felt it should have been taxed through PAYE and applied a charge and sent him a bill. As the client is abroad, in less than great health, he just wanted to settle and get it out of the way.
Having argued the point, HMRC relented and changed the clients bill to the tax return.
You have to wonder how much they get away with? Quite a lot, I reckon. What sort of people are they employing these days. Make sure you have someone on your side who will fight your corner.