Brits could reduce essential bills by as much as half using an easy Martin Lewis "three-week deadline" trick.
Millions could save hundreds every year with a quick web search.
Car insurance premiums are at record levels amid the spiralling cost of living crisis.
Some motorists have reported massive year-on-year hikes in their bills, with some seeing costs bumped up two or three-fold.
And things could get even worse based on rumoured changes to insurance premium tax in the upcoming Budget.
Fortunately, Martin Lewis has shared a simple hack you can use to beat the price spikes and keep bills manageable.
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Each year, thousands of drivers allow their insurance policies to renew automatically, rolling over to the next year with their current provider.
But Martin revealed that this is actually the worst way to handle a renewal and often leads to higher bills.
Instead, he urged car owners to manually renew - and explained exactly when to do so.
Speaking on his ITV show, the personal finance whizz said: "If you are near your renewal, getting quotes three weeks before may half the cost.
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"We ran 18 million quotes, it starts to drop at around 30 days, you get into the sweet spot around three to four weeks before.
"It bottoms out on average at day 23, and then the prices just start to rise and rise and rise.
"Everyone needs to get in their diary that 23 days before renewal because that's the sweet spot."
This is largely due to the way that insurers assess risk in clients.
Drivers who take the time to renew and research the best quotes are generally seen as more organised and less risky than those who auto-renew, Martin explained.
And it seems to really work as fans flooded the MSE boss with success stories.
One said the trick had brought their quote down from £1,500 to £650.
And a second claimed that he had managed to take the sting out of an £800 increase to his premium by reclaiming £618.
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Just bear in mind that Martin recommended shopping around as much as possible when you come to renew to find the best deal - even if it means changing insurer.
You can use the Compare+ tool on the MSE website to get an aggregate of the most attractive offers from major comparison sites.