Research has found out-dated online security checks is costing the UK travel industry one in five potential transactions, or £99 million of revenue annually.
The study, conducted by the International Fraud Prevention Research Centre on behalf of Experian, claims £470 million of online transactions in total were abandoned last year.
Most customers went on to complete a transaction on another site but a fifth opted to cancel their transaction completely.
The study drew its conclusions from a survey of 2,000 consumers, from studying ONS (Office for National Statistics) data as well as feedback from online retailers.
It found widespread frustration among consumers about old and inefficient identity checks, with some requiring the customer to submit physical forms or call a contact centre.
In some circumstances companies were found to be accepting a lower level of proof of identity leaving it open to fraud.
Nick Mothershaw, UK director of identity and fraud at Experian, said: "The UK's lost millions from inefficient online identity and security measures is a price that doesn't have to be paid given that technology now enables incredibly robust identity checks to be undertaken almost instantaneously.
"Older forms of identity verification - which draw on limited information or out-of-date data, cannot instantly validate as many genuine customers, and don't provide extra assurance from interactive questioning or the checking of previous identity fraud intelligence - require organisations using them to prioritise security or customer convenience.
"Those using less efficient identity checks can benefit significantly by upgrading to newer tools, which enable improvements in security levels and faster, less onerous checks."
Professor Paul Barnes, Director of the International Fraud Prevention Research Centre, added: "Depending on the reason for the identity verification check, our tolerance during a transaction varies greatly - and can be as short as a 60 second window.
"With millions potentially being lost from the key industries in the UK, it is vital that this issue is addressed as soon as possible."