The 2019 deadline
The FCA set 29 August 2019 as the final deadline for PPI complaints. Complaints submitted after that date are usually rejected without investigation.
This was preceded by extensive advertising to make people aware of the deadline.
Exceptions to the deadline
Very limited circumstances allow late claims: you did not know PPI was on your account (unusual but possible), you had ongoing complaints that were paused, or specific exceptional circumstances.
The Financial Ombudsman does not generally accept late complaints without exceptional reason.
Plevin claims
Plevin claims (excessive commission on PPI) had a shorter deadline that has also passed.
Plevin was a separate route based on undisclosed commission rates on PPI sales.
If you think you may have grounds
Contact the lender in writing. Explain why you were unaware or otherwise unable to claim in time.
If refused, the Financial Ombudsman route is available but success is unlikely without exceptional reasons.
Some claim management companies still advertise PPI services — most claims will be rejected. Do not pay for services unless you have a realistic reason to believe you have grounds.