Council tax bills will rise within the next couple of weeks. But before you worry about how much more you might be paying, consider this: you may already be paying too much.

Your bills are based on bands set on property values in 1991 - two years before the council tax was introduced. In many areas valuations were done in a hurry, often by estate agents driving past in a car.

According to Martin Lewis of moneysavingexpert.com, the system has more holes in it than a Swiss cheese. “I estimate that between 7 and 8 per cent of properties are in the wrong band,” says Martin, who has devised an easy way to check whether you are being charged too much.

“I would urge everybody to carry out this check. It takes 10 minutes to see whether you are owed a couple of grand - that’s got to be worth 10 minutes.”

So, knowing that in two weeks’ time council tax is set to rise by an average of 4.2 per cent in England and Wales and 2.5 per cent in Scotland, maybe you should be turning back the clocks and checking that your small, comfortable pad was not mistaken for a palace 16 years ago. Here, thanks to Martin’s research, is how you go about it: First check which council tax band your home is in: the cheapest are in band A and the most expensive in band H.

Then check which band your neighbours’ houses are in. To save you knocking on their doors, you can do it all online.

Log on to the Valuation Office Agency website for properties in England and Wales - www.voa.gov.uk - or the Scottish Assessors Association at www.saa.gov.uk for homes in Scotland.

Enter your postcode and check your band, then check the band for a similarly-sized property nearby.

If you’re in band F and your neighbours are in band C, say, then alarm bells should start ringing. Do a further check, though, before you reach for the phone. Go to www.nethouseprices.com and find out the most recent sale of a house similar to yours in your road.

Make a note of which quarter of the year the house was sold in. Then go to the Nationwide building society’s house price calculator - www.nationwide.co.ukhpi - and work out what your property was worth in 1991.

Enter the recent sale price in the “property value” field, date of sale in “Valuation date 1” and 1991 in “Valuation date 2”. Put “Q2” for date of sale, because the council tax banding took place in the second financial quarter of 1991, and press “enter”. If you get stuck, look at www.moneysavingexpert.com for more detailed guidance.

Now see where your 1991 house price puts you on the banding chart (see the chart to your right). If your jaw is dropping because both indicators show you are in the wrong band, it’s time to do something about it.

Don’t crack open the champagne yet, though. “Be very sure you have done all your research,” says Martin. “Never challenge speculatively.” For every property that should be in a lower band, there’s one that should be rated higher.

But Martin says that no one who has used his double-check system has been moved up a band. And of the thousands who have successfully challenged their banding, the biggest rebate so far has been pound;5,000.

If you are sure your banding is wrong, contact your local Listing Officer in England and Wales or your Local Assessor in Scotland. See www.voa.gov.uk

for more details.

You can write, phone or appeal online. Check the official list of reasons for revaluation and try to cite one of those. If your appeal is unsuccessful you can take your case to a tribunal at www.valuation-tribunals.gov.uk for England and Wales or www.saa.gov.ukvalappealcom.html in Scotland