HM Revenue & Customs is about to target up to £380m in unpaid tax from offshore bank accounts held by people living in Scotland, according to tax experts at accountant BDO Stoy Hayward.

As well as receiving a bill for unpaid tax, individuals could also find themselves with fines of up to 100% of the total unpaid tax owed.

HMRC was effectively given the "green light" to pursue tax liabilities from British residents' overseas bank accounts following last month's ruling by the Special Commissioners against four high street banks, believed to be HSBC, HBOS, Royal Bank of Scotland and Lloyds TSB.

Tax experts at BDO Stoy Hayward believe that up to 35,000 overseas bank accounts are held by people living in Scotland with around 400,000 acrossBritain.Allare expectedtobesubjectto HMRCinvestigationand some could face prosecution.

BDO believes HMRC could recover up to £275m following the ruling, in addition to the £4bn HMRC anticipate recovering from the decision against Barclays Bank last year.

Margaret Corless, director of tax and investigations at BDO Stoy Hayward in Scotland, said: "Anyone who holds an overseas bank account who thinks they can avoid paying owed taxes is going to be sadly mistaken.

"The most sensible option is to obtain professional advice and then approach HMRC voluntarily, as this is likely to result in a more sympathetic hearing.

"BDO Stoy Hayward understands that, for a limited time, HMRC is likely to reduce its investigators' workload by encouraging individuals with undeclared offshore accounts to come forward by offering a time window where reduced penalties of 10% of the maximum amount owed would be available. They would, however, still face a bill for up to 20 years of unpaid tax and interest."

Evidence presented by HMRC to the Special Commissioners in May 2006 indicated that up to 20% of offshore account holders were likely to be subject to a formal investigation, meaning that up to 7000 in Scotland are likely to becloselyscrutinisedby HMRC'soffshorefraud project group.

The amount of the fine will be based on an individual's circumstances but could be up to 100% of the tax owed with prison sentences possible for the most serious cases of continuing evasion.

Corless added: "The decision by the Special Commissioner to allow HMRC access to this information should not be underestimated by those holdingoffshorebank accounts. HMRC will follow up most cases and an investigation is not a pleasant thing to happen to anyone.

"We have already acted on behalf of people affected by the decision of the Irish banks to disclose details of their customers'offshoreaccounts. From our experience, HMRC appreciates people going to them voluntarily rather than them having to instigate an investigation."