If you are a medical professional who has not declared all of your income or capital gains, there is a one-off chance to do so with a fixed penalty of 10% of the tax instead of the normal 30% to 100%. This scheme was originally announced as applying to those regulated by the GMC, but it is now being extended to dentists and indeed all health professionals.
It doesn’t matter whether or not the undeclared income relates to your professional income. It also covers the situation where there is tax underpaid because you may feel that you have claimed too high a % of business use of your car.
You have to notify HMRC by 31 March 2010 of your intention to make a disclosure, and then actually do so by 30 June when the extra tax plus interest and the 10% penalty has to be paid.