Millions of people could make new PPI claims after court rulings found even those who were happy with their policies could be owed cash.
Tens of millions of PPI policies were sold to Brits over the years - often unfairly - attached to loans, credit cards mortgages and more.
People were told PPI would cover their debt payments if they died, become ill or disabled, lost their job or were left unable to repay debt for another reason.
The problem was that there were also a series of exclusions, meaning it was sold to people who could never claim on it, while commissions and profits were high.
In 2008 the regulator stepped in after thousands of complaints for people who had been mis-sold.
As a result of malpractice, over the past ten years more than £35billion has been handed back in compensation to mis-sold customers thanks to payment protection insurance.
That was all set to end in August last year, with a deadline set for claims, but new rulings mean even more people could be eligible.
The new cases are based on the amount of commission paid to banks by insurers, but not disclosed to customers.
Commission made up more than 95% of the policy’s cost in the most serious cases, The Sunday Times reports.
And that means even if you weren't mis-sold the policy, or have already claimed, you could get a payout.
Experts said recent claims made against banks could mean millions of new compensation claims, including from people who were denied payments, received only partial refunds or never claimed under the previous scheme.
That's because under the old rules, customers only got back half the commission the bank was paid, and these new cases have seen judges award far more.
NatWest lost a case earlier this year - despite it being past the official claims deadline - when Karen Smith, 58, from Cornwall, received an unsolicited refund from the lender worth £529.80, representing "a refund of commission over 50% charged on the PPI premiums paid".
As she didn't know she was paying commission, she took NatWest to court and won £1,500.
Bodmin County Court District Judge Jonathan Stone said the bank "provided no information to Mrs Smith that would enable her to discern that it would be receiving commission", but it knew how much commission it would receive.
"The inequality of knowledge was total and as a result, of course, the relationship was unfair," he added.
NatWest is appealing against the decision.
A NatWest spokesman said: "This case is the subject of an appeal and so it would not be appropriate to comment further."
Martin Richardson, from solicitors MoneyPlus Legal, said new claims against the banks could amount to "billions of pounds".
