Money saving expert Martin Lewis has revealed that anyone who has moved house since 1993 could be owed money due to overpaid council tax.
An investigation by MoneySavingExpert.com revealed more than £230million sitting unclaimed in 1.7 million closed or inactive council tax accounts across England, Scotland and Wales, the Mirror reports.
Martin Lewis, founder of the consumer website, said: "Councils are sitting on a staggering amount of money, at least £230m spread across 1.7 million accounts, which works out at an average of well over £100 sitting in each closed account.
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"And while councils do make efforts to track down those who are owed, many don't do it well enough, especially when people have moved out of their area and are no longer their responsibility.
"That means we all need to take responsibility for ourselves."
Owners of these 1.7 million council tax accounts should have been refunded when the account was closed.
The credit in them accumulates as households pay council tax a month or a year in advance, meaning it's common for people to have leftover credit when they move house.
Credit is also added if a person overpays their council tax bill, if a resident moves out, or if someone living in the property dies.
Who could be owed money?
MoneySavingExpert.com researchers believe you're most likely to able to claim a refund if you moved out of a local authority area in the last 29 years, and weren't paying council tax by direct debit.
The report advises anyone who moved house since 1993 to check if they are due over £100 due to the overpayments and credit.
The simplest and quickest way to check and claim is by filling out an online claims form from your old council.
Search the council name and the words 'council tax refund form' online, which should lead you to the correct document if it's available for that council.
Another way to check is by emailing, live chatting or calling the council - the details for which can be found on the Gov.uk website.
Are you on the right band?
MoneySavingExpert estimates around 400,000 homes in England and Scotland may also be overpaying because they are on the wrong council tax band.
Challenging your council tax requires a bit of research first and there are some risks involved - for example, you could end up discovering you’re in too low of a band and may end up paying more.
Before you consider challenging your council tax, you need to do your research first.
If it turns out you’re on too low of a council tax band, then you'll start paying a higher amount if your challenge doesn't go to plan.
Your neighbours will also be affected, if it turns out your entire street has been underpaying.
The first step to checking whether you're likely to be successful is to see what council tax band your neighbours are on.
You can check council bands online for free, so you don't need to ask your neighbours - just make sure you try and compare homes of similar sizes and value.
Use the GOV.uk website to do this for houses in England, or the Scottish Assessors Association for properties in Scotland.
This is only a rough guideline, so be warned that it could just be that your entire street is in the wrong banding.
Before going ahead with a challenge, you should also work out how much your property was worth in 1991, as this is when council tax was launched by the Government.
MoneySavingExpe rt has a free calculator tool to help you do this, as well as a table on what band you should have been put in.
Once you've done these checks, if you think you’ve got a good case on your hands you can contact the Valuation Office Agency (VOA) in England and Wales.
For home in Scotland you'll need to contact the Scottish Assessors Association (SAA) to submit your challenge.
Should you be successful, the valuation office will contact you and the band will be changed - and you’ll be due money back.
You can appeal to an independent valuation tribunal if you're not happy with the decision.
How to lower your council tax bill
The type of council tax reductions or discounts you could be entitled to depend on your circumstances.
Help offered also varies between local authorities, so it's best to get in touch with your council to see what you could claim.
For example, if you claim benefits - such as Universal Credit or Pension Credit - you could be entitled to up to 100% off your council tax bill.
Other situations where you could get money off include if you live alone or live with someone who doesn't qualify for paying council tax.
You'll typically get 25% off in these scenarios.
And the maximum 100% discount could apply to someone who has a severe mental impairment and lives alone, or if you live in an all-student household.
