Some 16 banks, believed to include nationalised lender Anglo Irish, have submitted details on offshore trusts, some located in the Isle of Man, to the Revenue Commissioners as part of its investigation into undeclared income.

The banks have been forced to report as third parties on any offshore trust settlements made in the period from December 2003 to April of this year. The Revenue would not comment on the identity of individual financial institutions but said they had received submissions from a "broad range'' of banks.

The Revenue said several of the banks were dealing with matters of a retrospective nature and consequently "an agreed structure'' for delivering details had been agreed.

"Returns from 16 financial institutions have, so far, been received and also further financial institutions have agreed a process of delivery to meet the reporting obligations,'' said a spokesman. Anglo Irish declined to comment on what the nature of its submissions might be, but it is understood the bank is co-operating fully with the investigations.

Meanwhile, it has emerged that Anglo Irish's Isle of Man operation provided a loan to an unnamed individual worth €51.4m which represented more than 10% of its enlarged capital base, forcing the company to provide a note about the transaction in its annual accounts.

The bank, which is a key deposit-taking operation for Anglo, the nationalised lender, has just five directors and 45 staff.

Last September the company changed its name from Anglo Irish Bank Corporation (Isle of Man) to Anglo Irish Bank Corporation (International) Plc. Anglo said last week it was not going to comment on relations with borrowers or dealings with the Revenue Commissioners. The offshore investigation being carried out by Revenue is into the transmissions of "assets and monies'' to and from offshore sources.

"The probing of the financial transactions and information further has revealed that the transfers and settlements of assets and monies on the structures represented a tax risk,'' the Revenue recently commented.

Legislation introduced in the Finance (No 2) Act 2008 requires third parties, such as, accountants, tax practitioners, solicitors and financial institutions to deliver certain information on settlements made by Irish resident and ordinarily resident persons involving non-resident trustees.

The investigation, which has only recently started, will target people who have not disclosed the existence of their trusts and offshore structures to Revenue and who have undeclared tax liabilities on the underlying funds.