If you think you have discovered an old tax bill that you haven’t paid and you’re wondering how long it might take HMRC to forget about it, read on.
If HMRC conduct an investigation into your finances, then they could chase any debts they discover up to 20 years after they orginally occured. It is not unheard of for HMRC to make mistakes like this, however it is extremely rare: they will normally investigate and take action within 4 years.
So, simply put, if you are expecting HMRC to forget about the debt and let you off the hook – they won’t.