Holidaymakers are being urged to use unspent vouchers worth £85 million before they lose financial protection.
This is the total value of unused refund credit notes (RCNs) given to customers by travel firms for package holidays cancelled due to the coronavirus pandemic, the Civil Aviation Authority (CAA) said.
The vouchers can be put towards the cost of a new holiday or exchanged for cash.
Any issued between March 10 2020 and December 19 2021 are covered by the Atol scheme, which means holders will not lose out if the company they booked with goes bust.
That protection expires on September 30.
Michael Budge, head of Atol, which is run by the CAA, said: “Millions of holidaymakers have missed out on travel over the past two years, with many being offered refund credit notes during the pandemic.
“As demand for travel continues to grow again, we want to make sure consumers are making the most of the financial protection available to them.
“If you have a refund credit note, make an Atol-protected booking or request a refund well before September 30 to avoid putting your money at risk.”
Consumers were legally entitled to cash refunds within 14 days for package holidays cancelled due to the virus crisis.
But many travel firms offered RCNs as an alternative to help their cash flow during the widespread disruption.