Britons are sitting on £4.25 billion worth of gift vouchers, credit notes, loyalty points and Airmiles.
About 83% of people have failed to cash in loyalty points and Airmiles or spend gift vouchers and credit notes, according to the financial website MoneyExpert.com.
And 57% of people have amassed points on reward credit cards that they have not yet spent, with these worth an average of £42.
Meanwhile 51% of people admitted they had a gift voucher they had not used, worth an average of £43, while 6% had credit notes averaging £163.
One in five people have amassed Airmiles worth around £35 that they have not used and a third of people are sitting on benefits averaging £32 from other loyalty schemes.
Sean Gardner, of MoneyExpert.com, said: "It's fairly typical for a company to offer customers an incentive to join their club. Whether it's reward points in a supermarket or Airmiles for choosing a specific airline, loyalty is meant to pay.
"However, our research shows that while these schemes are a clear incentive to buyers, we as customers do not fulfil our end of the bargain and spend our hard earned rewards. Which means providers have won twice by getting your business and then not having to reward your loyalty as agreed."