According to HM Revenue and Customs 650,000 people have still failed to file their 2010/11 SA returns. From 1 May 2012 they will receive daily penalties of £10 per day. That is £6.5 million in penalties per day.

HMRC has produced a flow chart designed to enable taxpayers decide if they should complete a 2011/12 tax return. This indicates that you should only file a return if HMRC writes tells you to. However, the onus is also on taxpayers to notify HMRC if they have untaxed income.

All penalties may be appealed to the First Tier Tax Tribunal. There are time limits for appeal, and the taxpayer is required to prove that they have a reasonable excuse for not filing a return on time and have subsequently done all they can to file the late return, see How to appeal against a tax penalty.
At the beginning of the month HMRC revealed that they have sent out 12,000 penalty notices to the wrong people.

For information on penalties and appeals click on: Penalties & Compliance