Yesterday's ruling by the High Court represents one of the largest successful tax assessments by the Criminal Assets Bureau.
Officers from the CAB have estimated that Mr Thomas McDonnell was making £5,000 a week with an average of 12 prostitutes a day working for him.
The CAB investigation into Mr McDonnell's business dealings began in 1997, and the £1.75 million tax ruling relates to his alleged earnings since 1988.
Mr McDonnell (46), from Cooraclare, Co Clare, has five criminal convictions. He was first convicted in 1975, at age 22, for common assault.
He was convicted on three further occasions for burglary and larceny and in June 1991 was convicted of making a living from immoral earnings. He was fined £4,500 for the offence.
A file on Mr McDonnell's alleged brothel-keeping has been sent by the CAB to gardai in a city-centre station to investigate the allegations with a view to a criminal prosecution.
Mr McDonnell began his working life as a builder, refurbishing houses in Dublin. In 1987 he bought a house in Cabra, Dublin, with a mortgage of £31,000. That was sold in 1993, and the following year Mr McDonnell bought another house in Stephen Street, Dublin. This was also sold in 1996 at more than double the 1994 price.
Women have said that they paid Mr McDonnell a £20 fee for each client. Gardai have identified four premises, three in the city centre and a fourth in Rathmines, which allegedly were run by Mr McDonnell. The services were advertised in In Dublin magazine.
Mr McDonnell is believed to have owned the Rathmines premises, and one other premises in the city centre. He was evicted recently from another city-centre premises after publicity surrounding his alleged activities as a brothel-keeper.
In 1993 he bought a helicopter for £170,000, and rented a hangar space from a commercial helicopter company in Dublin. He regularly used the helicopter to fly down to his family home in Cooraclare, before selling the helicopter in 1997.
The £1.75 million tax assessment was served on Mr McDonnell in July 1998. The tax demand is the second-largest assessment made by the Criminal Assets Bureau since it was set up. A High Court appeal is pending against the tax demand of £2.5 million from a Cork man, Mr Patrick McSweeney.
Mr McDonnell is expected to appeal the judgment.
