Households in the wrong council tax band could be due thousands of pounds of refunds for overpayments.
Here's how to get your money back.
How it works
The council tax system was established in 1993 and properties were placed in bands from A to H, based on valuations in 1991.
While homes in Wales have since been revalued, properties in England and Scotland haven't.
If you can prove your property is in a higher band than it should be, you can reclaim overpayments, often backdated to 1993.
Check your banding
You'll need to find out if your house is in the right band by checking the banding and value of your property and comparing it to your neighbours.
Enter your postcode at the Valuation Office Agency website (https://www.gov.uk/council-tax-bands) to find out your council tax band, then check the bands of neighbours with similar houses to yours - they need to be roughly the same size and age for an accurate comparison.
If you don't know the value of your home, you can find out what similar properties in your local area have sold for recently by visiting Zoopla or Rightmove.
Next, you should work out what your home was worth in 1991 by using Nationwide's house price calculator.
Now you'll need to compare this figure against the council tax bands - which will be available on your local council's website or at www.direct.gov.uk - to see if your banding is correct.
Challenge your banding
Double-check the previous steps, because the reassessment you will be asking for could actually place you in a higher band. If you do believe your banding is unfair, contact your local valuation office for a proposal form.
You will need to send your valuation office evidence, including house prices for addresses of up to five similar properties in a lower Council Tax band than yours.
If you do not agree with their decision you can still challenge your band by finding your property on the valuation office website and selecting your address.
You can then select a link if you think your tax band is wrong and provide evidence if you wish to make a challenge.