New legislation called ‘Requirement to Correct’ requires UK taxpayers to notify HMRC about any offshore tax liabilities relating to UK income tax, capital gains tax, or inheritance tax.

So if you generate interest from a foreign bank or savings account or overseas shares, rent from a holiday home, or income or gains from a trust abroad, you have until 30 September to declare it.

The deadline coincides with the date more than 100 countries will exchange data on financial accounts under the Common Reporting Standard.

Chris Davidson, chair of The Chartered Institute of Taxation’s Management of Taxes Sub-Committee, said: “HMRC will soon be receiving a huge amount of information from other tax jurisdictions and we have been left in no doubt that they will use it to launch investigations and, in some cases, criminal prosecutions against individuals who have not made a correct and complete declaration of their offshore income and assets to the UK tax authority.

“The days of HMRC being ‘in the dark’ about UK taxpayers’ offshore bank accounts and other interests are over.

“This makes it all the more pressing that taxpayers check their positions now to ensure that they minimise their risk of receiving a penalty for failing to correct, or worse, put themselves at risk of a criminal prosecution.”