HMRC have made it clear that they do not send taxpayers emails regarding their tax affairs. So the next time you receive an email purporting to be from HMRC you can safely bet that it is a scam and that it can be safely ignored. Whatever you do, do not follow any links in these emails as they will likely lead to all sorts of computer viruses infecting your computer. And do not provide any personal information, particularly bank details.
If you are in doubt as to authenticity of communications received call HMRC to clarify.