The Haughey family agreed to pay a €5 million tax bill in March this year, and may draw on the funds realised through the sale of Abbeville to settle this and other debts.
The €5 million tax, interest and penalties bill arose on foot of investigations by the Moriarty tribunal.
It comes in addition to a €1.3 million settlement Mr Haughey made in 2000 arising from payments to him discovered by the McCracken (Dunnes Payments) tribunal. The total tax bill arising from the two tribunals for Mr Haughey is, therefore, €6.3 million.
When the deal was reached, the Revenue was assured that the €5 million bill was capable of being funded from "Haughey family resources", according to sources.
The Moriarty tribunal is still sitting but has not discovered a new payment to Mr Haughey for some time. It is considered unlikely that it will discover fresh payments at this stage but, if it does, then a new tax bill could arise.
The tax bill comprises €2.47 million in tax and €2.53 million in interest and penalties, and follows lengthy negotiations between Revenue officials and Mr Haughey's advisers.
Mr Haughey and his wife, Maureen, own their family home, Abbeville, and surrounding acres at Kinsealy, Co Dublin, but transferred the bulk of the 250-acre estate to their four children, including Mr Seán Haughey TD, in 1990. In 2000, 10 acres of the Kinsealy land were sold to developer Treasury Holdings for €7.62 million.
Negotiations between Mr Haughey and Treasury over the outright purchase of the Abbeville estate ended unsuccessfully late last year.
The tax implications of the latest deal revolve around Capital Gains Tax (CGT), which arises when someone sells an asset that has accumulated value during the term of ownership. The amount taxed is the difference, if any, between the selling price and the cost price, indexed to allow for inflation.
The rate of CGT is now 20 per cent, having been reduced from 40 per cent in 1999. The CGT liability on an asset originally received as a gift would be significantly more than on bought assets because there is no cost on the gift.
As the house is Mr Haughey's principal private residence, he can take his profits on the sale of the house and one acre tax-free; no CGT applies on the sale of a family home and one acre of land. He would be liable for CGT on the rest of the land sold. The profit on this portion of the sale would be taxed at 20 per cent.