MANY householders will be poorer in two weeks' time, particularly in the Dublin catchment area. The reason? October 1st, the deadline for paying the Residential Property Tax (RPT), is fast approaching.

The tax is even more invidious this year because the threshold for the market value of houses has not kept pace with the rise in house prices. The whole idea of thresholds was that house owners should not be penalised because of escalating house prices. It is not working.

The Finance Acts provide for an automatic adjustment of the market value of houses and income thresholds for the tax. These are based on the index of new house prices and the consumer price index. Fair enough, but the way it is being implemented is inequitable because the Revenue Commissioners have used the housing statistics for December 1995 to adjust their threshold for the value of the property, whereas householders have to use April 5th 1996 as the valuation date.

The application used by the Revenue would be reasonable if prices were static. However, in a market with rapidly rising house values, it certainly is not.

The statistics speak for themselves. The market value of a person's home has to be over £101,000 before the tax becomes payable this year. That is 7.45 per cent higher than the previous threshold of £94,000.

The tax is payable if the total income of the household exceeds £31,100 (there is marginal relief up to £40,100). That is 2 per cent higher than the threshold of £29,500 in 1995.

No one could grouse about the new income threshold. After all, the annual rate of inflation to mid May (the nearest date to April 5th) was 1.4 per cent and it was not much different, at 1.5 per cent, in the year to mid August.

However, the threshold for house values is very different. The April 5th date straddles the first and second quarter figures. The latest housing statistics, published by the Department of the Environment, shows the following relevant trends in house prices:

new house prices, between the first quarter of 1995 and the first quarter of 1996, rose by 4.9 per cent;

. new house prices, between the second quarter of 1995 and the second quarter of 1996, increased by 10.5 per cent;

. second hand houses rose at a faster pace this year - by an annual 10.2 per cent in the first quarter, and by an annual 15.2 per cent in the second quarter;

. the price rises equate to the 10-15 per cent often quoted by auctioneers, particularly in the Dublin area where in a three month period (second quarter, 1996), prices of new houses increased by 5.8 per cent and by a staggering 11 per cent in the second hand house sector.

The threshold for the value of houses is blatantly inadequate. But everything about RPT is invidious. The inequities, often cited, include an indictment against the tax because it is on the gross value and takes no account of the mortgage against it. House improvements will result in a higher value and therefore a larger RPT. A large rural house may escape the tax where a similar house in an urban area would be taxable, and so it goes on.

But a new anomaly involving people who have PAYE income and Schedule D income, has emerged. In the good times both incomes are added to bring the total income above the threshold. Fair enough. But when there are losses on Schedule D (Lloyds underwriters, for example), incredibly, they are not deductible against the PAYE income. The Revenue explains that legislation, under the Finance Bills, prohibits an offsetting of Schedule D losses. This is a ludicrous situation.

The bias against house owners in the Dublin area is further highlighted by a breakdown of RPT for last year, showing a £9.5 million RPT payment by 19,500 householders, with Dublin householders accounting for a whopping 74 per cent of the number of taxpayers, and 77 per cent of the value.

The yield from RPT has risen from £1 million in 1983 to a peak of £14.2 million in 1994 before falling to £12.1 million in 1995 (£9.5 million paid plus £2.6 million in arrears), due to a change in the exemption limits.

With rising house prices it could well reach a new peak this year.