When it comes to sole trader accounts and personal tax returns, it pays to be on the ball. This is especially true when it comes to filling in your annual self-assessment tax return as a sole trader. Not paying close attention to this key business task can see you land in hot water with HMRC and face stiff penalties. Very often, it is actually helpful to see what common mistakes other sole traders make, so you can avoid them. But which are normally seen time and time again?