YOUR council tax is based on the approximate value of your house.

Or more precisely, it's based on what your house was or would have been worth in 1991. So if you are about to spend the weekend house-hunting, you may wish to look away now.

In 1991 barely 12,000 properties in Scotland - out of 2.4 million - were valued at more than £212,000, the threshold for the highest council tax bracket, Band H. That is now the average price of a house in Edinburgh. At the other end of the scale more than 500,000 households were living in properties worth less than £27,000, the valuation for Band A. More than half of all homes in Scotland were worth less than £45,000. It wouldn't buy you much these days.

Apologies, house-hunters, but I've dredged up the figures to illustrate a point made by the Institue for Fiscal Studies in a recent study: Council Tax is "Ripe for Reform", as the think tank put it. Properties have not been revalued and bands have not been adjusted since the system was introduced as a hasty replacement for the community charge/poll tax nearly a quarter of a century ago. Ever since then, progressive opinion has regarded the council tax as unfair. Yes, folk in bigger houses paid more - but they still seemed to be getting a good deal compared with those in the most modest homes. But as this column discussed last week, successive Holyrood administrations have singularly failed to come up with reforms that would command political consensus or win public acceptance.

Figures revealed in yesterday's Herald renewed calls to do just that. The previously unpublished Scottish Government statistics showed that since council tax bills were frozen in 2007/8 (originally as a stop-gap measure until the SNP's local income tax (LIT) system could be introduced) people in Band H homes have saved £1535 compared to just £258 for those in Band A properties. Continuing to freeze bills hasn't addressed the unfairness in the system, it's argued, while council budgets are increasingly squeezed and services cut. It has been reported as fact in some quarters that when the SNP open up discussions about a possible alternative to the council tax, as they've promised to do before the next election, ministers will simply come back with a tweaked version of LIT, shelved in 2009 amid claims it was unworkable.

The assumption is based on the SNP's manifesto promise to develop a system "based on ability to pay", the language they used to use to promote LIT. In fact ministerial thinking on the issue is a little more flexible, according to senior sources. A relaunched LIT has not been ruled out, and ministers remain attracted by an income-based levy, but "ability to pay" will be interpreted in the wider context of other tax powers coming to Holyrood, either those already on the way or as a result of independence. What this wait-and-see approach also means - disappointingly for those urging reform - is that we'll not see the SNP's proposals until close to the 2016 Holyrood election.

In the meantime it would be surprising if the SNP did not want to keep their options open, especially with so much advice on the table. The IFS, in their "Taxing an independent Scotland" report last month, cautioned strongly against moving away from a tax on property in the event of a Yes vote. Rather, the think tank argued, both an independent Scotland and the rest of the UK, sharing an open border and closely aligned economies, should rely more on property tax. As an "immobile tax base" it would reduce opportunities for people to move their tax liabilities between the two countries.

Another recent report, from the Scottish Government's own Fiscal Commission, made the point that setting "local" taxes centrally - one of the criticisms of the original LIT plan - could damage local decision-making.

Apart from such technical considerations there is another powerful reason why SNP ministers might want to keep their options open: the new system, whatever it may be, should be built to last for 20 or 30 years. Inevitably governments of different political stripes will have to administer it at one time or another and that means there will have to be a degree of political consensus. Calmer heads in the SNP and Labour are coming to realise that. It's a hopeful sign that reform, if not imminent, is possible.