Several financial institutions will have to make additional DIRT settlements with the Revenue Commissioners. National Irish Bank (NIB), Irish Life & Permanent and another 35 banks investigated by the Dail Committee of Public Accounts face additional bills for the years since 1999.

They have already paid £173 million (€220 million) for the period from 1986 up until 1999, when the committee began a hearing on the widespread use of bogus non-resident accounts by Irish residents.

They now have to settle liabilities for the period from 1999 until they regularised the situation regarding non-resident accounts.

Mr John Trethowan, project director with NIB, said yesterday the bank had recently approached the Revenue Commissioners with an offer. A spokesman for Irish Life & Permanent said it also expected to make a final settlement in respect of the years 1999/2000 and 2000/ 2001.

NIB paid £5.25 million previously. It expects to pay only a fraction of that - less than £100,000 - for the period from 1999 onwards. The Revenue Commissioners confirmed yesterday they planned to carry out follow-up audits in respect of the two subsequent years. The need for a second payment arises because the first settlement was reached using only a sample of accounts. The settlement amounts were calculated by extrapolating from the sample rather than checking every account to see if it was genuine. As a result, a significant number of bogus non-resident accounts were undetected by the process. DIRT continues to be owed on these accounts from 1999 until they were regularised by the banks' own investigations.

The second-round payments will be on a much smaller scale than the initial payments. The largest settlement was made by AIB, which paid £90 million in respect of the years from 1986 to 1999. AIB originally estimated its DIRT liability at £35 million. A spokeswoman for AIB said yesterday that the bank's compliance levels were extremely high. "If something is identified, we will deal with it as appropriate," she said.

If AIB has to make another settlement with the authorities, the amount could run into millions.

Bank of Ireland made a £30.5 million settlement in July last year, having estimated its liability at £2.8 million. The bank declined to comment yesterday on whether it might make an additional payment.

NIB has disclosed that it will make an additional settlement as part of a process aimed at informing the public on the measures the bank has taken to improve corporate governance in the wake of the DIRT and other scandals. As well as offering bogus non-resident accounts, the bank was also found to have overcharged some customers and mis-sold to others insurance policies which were used to evade tax.

Since January 1998, when the first scandal broke, the bank had spent £17.5 million on putting in place new procedures and structures to make sure the errors were not repeated, said Mr Trethowan.

A dedicated investigations unit of up to 40 people has been working on the project. More than one million pages of text have been provided to investigating agencies, including High Court-appointed inspectors and the Garda. The High Court inspector's report is due later this year.

NIB is also trying to reach settlements with the 470 purchasers of offshore investment products, including Clerical & Medical International bonds. Many of the purchasers had subsequently made large payments to the Revenue Commissioners in respect of tax owed on the money invested in the bonds.

To date, the bank has made 20 settlement offers totalling £400,000. Customers have accepted offers in five cases; another 15 offers are still live.