Holidaymakers are being urged to use £132 million worth of unspent vouchers before they lose financial protection.
The Civil Aviation Authority (CAA) said the total relates to refund credit notes (RCNs) which were offered by many travel firms as an alternative to cash refunds to reduce the impact of the coronavirus pandemic on their finances.
The vouchers can be used towards the cost of a new holiday or exchanged for cash.
Any issued from March 10 last year which relate to package holidays are covered by the Atol scheme, which means holders will not lose out if the company they booked with goes bust.
Travel firms will no longer be able to issue Atol-protected RCNs from December 20, and the financial protection of existing vouchers ends on September 30 next year.
Michael Budge, head of Atol, which is run by the CAA, said: “With over £130 million of Atol refund credit notes yet to be redeemed, and international travel opening up again, we want to remind consumers to redeem any unused credits to make sure they do not lose out.
“Refund credit notes have been a fantastic tool to reassure consumers and support the industry.
“The decision to end the scheme reflects the changing of international travel restrictions with significantly increased demand from consumers over recent months due to the opening up of more destinations.”