Over the past 10 years, the “offshore” banking landscape has been substantially transformed and countries like Switzerland, which even ten years ago could not consider disclosing any details of its customers, now freely send bundles of information to overseas tax authorities on an annual basis. As a result, many people in the UK who had bank accounts and assets overseas have now declared them to HMRC and regularised their tax affairs. However the tax authorities worldwide are now actively looking for people who are not complying with the new regimes and there is still plenty of work to do. Here are my top three tips you should be thinking about with regard to overseas assets, even if you think you have nothing to declare.

On September 30, 2018, the last remaining advantageous programme to disclose overseas tax irregularities will effectively come to an end. It will still be possible to disclose offshore income after that date but under much less favourable terms.

HMRC has promised penalties of up to 200 per cent and new criminal sanctions from October. These threats are forcing people to rethink issues they previously considered did not need disclosing and we are seeing a surge in activity of people registering with HMRC as the deadline approaches. If this applies to you, please do not leave it until the last minute; speak to your accountant or a specialist adviser now.

Secondly, exchange-of-information programmes with overseas tax jurisdictions are in full swing. More than 100 countries have signed the common reporting standard (CRS) and have started, or will shortly be starting, to share information about accounts and other investments held by residents of these countries. For example, if you are a UK resident and you have a bank account in France, you can expect the French government to regularly send information about that bank account to HMRC.

America has not signed up to the CRS, but has its own rules (as it so often does) under the acronym FATCA (Foreign Account Tax Compliance Act). Everyone needs to take a crash course in filling in FATCA compliance forms. Many people have already been asked by UK banks to fill in American tax forms under the programme. Sometimes the appropriate form is simply to confirm the account holder has no connection whatsoever to the United States.

However these forms are complex and not written in language which is familiar to even the financially trained UK person. Once the forms are sent to the customer, the bank will soon threaten to close your accounts if they are not completed.

You can find some FATCA guidance notes on the internet but, given the complexity of the forms, the situation remains unsatisfactory.

Therefore, if you have any overseas accounts, remember they need declaring, possibly both in the place where you live and the country where the asset is held. The tax authorities will automatically have information about these assets, so do not forget to fill in the correct tax returns.

Thirdly, if you are an American citizen you may have a whole other area of concern. Unlike the UK, which taxes only people who live in the country or have assets there, America taxes citizens wherever they live in the world. That means every USA citizen should be filing American taxes, even if they have not lived in the States for years. Many American citizens have still not taken care of this, as they may be unaware of the rules, compliance is complicated and expensive and often no tax is due.

However with the FATCA exchange of information, the IRS will know where all American citizens are living and will be looking to bring them back into the tax net. While this is not my area of expertise, there are amnesty programmes available to help American citizens regularise their tax affairs and the consequences are not too unforgiving, as long as the disclosure is voluntary. Waiting until the IRS finds you is a high risk strategy.

So while many people have brought their UK taxes up to date, there is now an ongoing need to review your income and assets to ensure you are complying with all overseas laws in addition to local legislation. Failure to file the correct tax returns is much more likely to give rise to a tax inquiry. And if you think HMRC is tough, just wait until you have to meet the IRS.

Geoffrey Hollander is head of tax investigations at Cameron Baum Chartered Accountants, 020 7724 8824