Martin Lewis has urged Brits to check if they're due a council tax discount after one woman claimed back £15,000.
The MoneySavingExpert has warned that you could be missing out on hundreds - if not thousands - of pounds.
There is a "worrying number of people" missing out on savings, and many may not even be aware that they are.
Those categorised as being "severely mentally impaired" may be missing out on cash.
According to Gov.uk, severe mental illness "refers to people with psychological problems that are often so debilitating that their ability to engage in functional and occupational activities is severely impaired".
This can come from health issues including - but not limited to - dementia, learning difficulties, brain injuries, strokes and more.
You would need to receive a medical note from your doctor to certify your condition.
Writing in the MoneySavingExpert newsletter, Martin said: “I started banging the drum on the severe mental impairment council tax discount in 2016, as it seemed a worrying number of the country’s most vulnerable were missing out.
"Soon after, we did detailed research which showed it was a postcode lottery – with people 77 times more likely to get it with some councils than others – and ‘mystery shopping’ that showed 68% of frontline staff didn’t or couldn’t explain it properly.”
This comes after a 98-year-old woman received a £15,000 council tax refund and had her future bills cancelled as she had vascular dementia.
Her son, Graham, was encouraged by his wife to apply for the SIM discount on behalf of his mum. And just 10 weeks later, his mother received the giant refund.
Money Saving Expert campaigns lead Katie Watts went on to explain: “This council tax discount is rightly meant to help some of the most vulnerable in our society and this is one of the biggest backdated reclaims we’ve seen.
"Being refunded £15,000 is astonishing, and just goes to show how long this discount can go unclaimed for.”
Many councils will backpay any council tax that was overpaid but not all of them will, warns the site.
The advice from the Money Saving Expert team came in the wake of households being informed that their council tax bills go up under plans announced in Jeremy Hunt's Autumn Budget.
In yesterday's budget was a clause in which the cap on the level of council tax rises could be increased to 5%, up from the current 2.99%.
This could mean on average, council tax increases for some households of between £115 and £166 a year, taking the total annual cost to around £2,400.
