In some complex cases it was also possible to negotiate with HMRC over the repayment date.

However, Gary Ashford, tax investigations director at Grant Thornton, says that while it is likely that there will be a late influx of payments this month from those wanting to avoid the heavier penalties, HMRC will be somewhat disappointed with the amount of revenue generated.

"It was initially thought billions could be recovered. It's now likely to be more like millions that will surface," Ashford explained, continuing: "It may even be a case of HMRC having overestimated how many people hold undisclosed offshore accounts."

He went on to add that: "However, it looks like HMRC are about to embark on a second amnesty. They are already targeting another group of around 150 financial institutions in a bid to gain customer details. Given the existing legal rulings on the large banks it seems likely that HMRC will be successful in obtaining customer information relatively quickly. HMRC is determined to make examples of tax dodgers but will be looking to encourage them to disclose as they did with the Offshore Disclosure Initiative."

Whatever the case, Ashford is advising those who have yet to come forward to do so or risk hefty tax bills.

"One hears of anecdotal tales of individuals moving their funds to ever more exotic locations to avoid HMRC, but given the international cooperation taking place between tax authorities in relation to the exchange of information, it seems only a matter of time before the taxman catches up with them. Anyone concerned should seek financial advice from a tax expert sooner rather than later," he concluded.