6,000 Britons who hold money in the Swiss arm of HSBC will soon receive a letter telling them that they need to own up to unpaid tax. The bank is acting on information received last year under a tax treaty. This revealed that more than 6,000 individuals, companies, trusts and other bodies held accounts and investments with HSBC Geneva. HMRC has already begun criminal and serious fraud investigations into more than 500 individuals and organisations holding these accounts. HMRC will shortly be writing to those who have not yet come forward, or are not under investigation. They will be offered a chance to contact HMRC and disclose all their tax liabilities, HMRC said. Fines of up to 200 per cent of any tax may, in certain circumstances, be imposed on people not coming forwards during this window for disclosure. "This is not an amnesty. There are no special rates of penalty or interest for those who come forward voluntarily," said HMRC's Dave Hartnett. "This is an opportunity for those who have made errors in past returns to correct them. The net is closing on offshore evaders. Don't wait for HMRC to contact you."