New rules came into force on 7 October 2017 creating three new strict liability criminal offences regarding failure to disclose UK tax liabilities arising from offshore assets, income or activities, where the unpaid or underreported tax is over £25,000. The specific offences are: failing to notify HMRC of chargeability to income tax or capital gains tax; failure to deliver a return when required to do so by a notice issued by HMRC; and filing an inaccurate return. The new rules apply to tax years commencing 6 April 2017, which means the earliest an offence of failure to notify can take be committed is 6 October 2018; for failure to file a return the earliest date is 6 April 2020; and for inaccuracy in a return, 31 January 2020.

Failure to comply may result in a fine or a prison sentence unless the taxpayer can prove that they took reasonable care or had a reasonable excuse for their non-compliance. The offences don't apply to trustees or personal representatives.