He warned that car insurance prices could rise by as much as 50 percent if drivers leave them later than three weeks before their current policy expires. Martin Lewis explained that the low prices are due to the insurers’ perception of risk towards the drivers.

He said those who are prepared and update their policies are considered “low risk” compared to those who leave them until the last minute.

He also revealed two success stories from drivers who followed the tip and made massive savings.

Speaking on the Martin Lewis Money Show, he said, “Last week it was all about big changes in auto and home insurance and why you should check your prices now as they could go up in January.

“The 21 day rule is, if you line up to renew, this is the sweet spot to get your offers, your new offers.

READ MORE: Martin Lewis Says Drivers Can “Save” By Updating Job Descriptions

Bob said, “When my insurance needed to be renewed in early November, I followed Martin’s advice and started checking other websites.

“I just signed with AA for half the price I paid for this year’s price and saved nearly £ 300.”

Angelica said many other drivers have benefited from the 21-day rule as well.

She read another message from Netti that confirmed she had saved hundreds by following the simple tip.