The Financial Conduct Authority (FCA) has set a deadline before which new payment protection insurance (PPI) claims must be brought for 29 August 2019.
The regulator will run a two-year consumer communications campaign from August 2017 to help consumers decide whether or not to bring a claim.
It has also made final rules on how firms should handle complaints based on a Supreme Court judgment in Plevin v Paragon Personal Finance Ltd (Plevin).
This gives consumers new grounds to complain if the provider failed to disclose the commission it received for the sale.
The FCA said it will require all firms to write to previously rejected complainants who are eligible to complain in light of Plevin in order to explain the new basis for complaining to them.
Complaints about PPI policies sold after 29 August 2017 will not be subject to the deadline.
Chief executive Andrew Bailey said: "Putting in place a deadline and campaign will mean people who were potentially mis-sold PPI will be prompted to take action rather than put it off. We believe that two years is a reasonable time for consumers to decide whether they wish to make a complaint.
"We have carefully considered the feedback we received and we still believe that introducing a deadline for PPI complaints and a communications campaign warning of the deadline will benefit consumers."
PPI is a multi-billion pound insurance misselling scandal, which has so far led to a raft of banks being fined and redress payouts exceeding £20bn.
PPI was sold to borrowers alongside credit products. It was meant to help repay some or all of their borrowing if they lost their income for a period, however many of the policies sold were later found to be unsuitable.
The most commonly sold types of PPI were single premium policies on unsecured loans (about 48% of all PPI policies sold), credit card PPI (36%), and regular premium policies on loans or mortgages (15%).
Complaint time limit not triggered
The complaints handling rules already set time limits for consumers to make complaints about financial products.
These time limits are generally six years from the event the consumer is complaining about or three years from when the consumer knew they had cause to complain.
In the case of PPI, because many consumers did not know they had been mis-sold PPI, these time limits may not yet be triggered, the FCA said.
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