They apply from 6 April 2011 to Income Tax and Capital Gains Tax. The first Self Assessment returns affected are for the 2011-12 tax year, with paper returns due by 31 October 2012, and electronic returns by 31 January 2013.
The penalty does not apply if you provide HMRC with an accurate account of your income tax and capital gains tax liabilities. That includes any income or gains from an offshore account or asset unless you have no additional tax liability from them.
Read more from HMRC by downloading their paper on Offshore Tax Evasion Penalties.