Tough times: Council tax is a big part of many people's monthly essential bills (Mahood cartoon for the Daily Mail)
If your house is in the wrong council tax band, you may be entitled to cut your council tax bill and win a refund windfall.
Most English and Scottish homes were put into council tax bands in 1993 and have not been reassessed since.
But official figures show that since that time one in 20 homes have been found to be in too high a council tax band. Anecdotal estimates suggest many more homes may be in the wrong bracket, claiming valuation was left to a haphazard and error-ridden system based on guesses by estate agents.
How much extra could I be paying?Someone whose home was incorrectly placed in Band E rather than D, for example, has been paying 22.2% too much since 1993.
For someone living in St Albans this equates to £327 for the year 2012 to 2013, for someone living in Birmingham it is £281.
If you are successful you should have your bill reduced and may get a refund backdated to when you moved into the property.
The backfiring council tax claim Challenging your council tax could get you a windfall rebate but beware John Pigden complained and officials raised the neighbours' bills
What can I do?
If you home is in the wrong band you are able to ask for reassessment and you might pay less, and you may also receive a rebate. But be warned - you could also see your bill rise, especially if your home has been extended or converted.
The Valuations Office Agency says 4.3%, or 903,000, of the 21m homes in England had their council tax band reduced in 15 years after 1993.
The main sign homes are in the wrong council tax band is that they substantially differ from other properties in the same vicinity, or have been converted from larger homes.
People who believe they may be in the wrong band should check what neighbours in similar properties are paying and can use a house price calculator to estimate their home's approximate value in 1991.
Who do I contact?Banding appeals can be made at the Valuation Office Agency, in England, or the Scottish Assessors Association, in Scotland.
If you think you might be in the wrong band, compare your banding with similar properties in the neighbourhood.
You can check on voa.gov.uk or call 03000 501 501 in England, 0300 050 5505 in Wales, or contact the Scottish Assessors Association (saa.gov.uk or call your local office).
If you then suspect you are paying too much, contact your local VOA or SAA office and explain why you think that your bill is incorrect. It will take about 30 working days for it to let you know the outcome.
If it agrees the band is wrong, it will change it. The service is free and your council will then update your tax bill. And you will have any previous overpayments refunded.
You may be informed that you are unable to challenge your band, as you have lived in the property more than six months.
However, don't give up. There is a legal obligation to ensure properties are in the right band, so you should insist on a check and explain why it is required in a letter.
If the Valuation Office still turns you down you can go to the Adjudicator's Office.
HOW COUNCIL TAX BANDS CHANGED Band 1991 value 2013 value Council tax bands and Nationwide BS average UK house prices Jan to Mar 2013 (Thisismoney.co.uk April 2013) A Under £40,000 Under £120,000 B £40,001 - £52,000 £120,000 - £155,500 C £52,001 - £68,000 £155,500 - £203,000 D £68,001 - £88,000 £203,000 - £263,000 E £88,001 - £120,000 £263,000 - £358,500 F £120,001 - £160,000 £358,500 - £478,500 G £160,001 - £320,000 £478,500 - £956,500 H More than £320,000 £956,500 plus Work out how house prices have changed in your area with Nationwide's historic house prices calculator