The company that operates the Octopus smart card is holding HK$3.3 million from 35,000 cards lost since 2008.
In response to complaints by people unable to reclaim lost cards, Octopus Cards said the deposit and remaining value of a lost card not encoded with the holder's details could be refunded only if users provided details of previous transactions as proof of ownership.
An Octopus spokesman said customers could call the company's hotline - 2266 2222 - or submit a written request to check whether a lost card had been found.
To date only 30 people who lost non-personalised cards have had them returned since 2008. It was earlier reported that a person who informed Octopus of a lost card was told the company did not have a service for returning them when found.
Octopus Cards says around 95 per cent of the seven million people in the city use the cards, and about 21 million have been issued. Lost cards encoded with an owner's details, such as those which are credited automatically, are returned when found.
An Octopus Cards spokesman said owners of non-personalised cards could reclaim lost cards only by providing 'valid proof such as transaction receipts evidencing the use of the card to help verify the identity of the owner'.
He said all cards, even those not encoded with a holder's personal details, retained transaction records that might help to identify the owner.
The spokesman said the company kept lost cards that were handed in, and kept the deposit and remaining value until the cards could be reclaimed by the owner.
Since 2008, the company had accumulated about 35,000 lost cards lacking owners' details. The deposits and remaining value of these amounted to about HK$3.3 million, the spokesman said.
Independent lawmaker Andrew Cheng Kar-foo said that if the cards were not reclaimed after a set period Octopus should consider donating this money to charity or use it to upgrade its operating system, which he said had repeatedly suffered technical problems.
Octopus Cards was widely criticised last year for selling customers' personal data to third parties for HK$44 million.
One man complained about what had happened after he found a non-personalised Octopus card and gave it to the police. According to police procedures for handling lost property, any item that does not include personal data and is unclaimed after three months may be claimed by the finder.
But when the man tried to claim the card after three months he was told that it had been handed to the Octopus company.
A government spokesman said yesterday that lost cards would not be given to the finders because of concerns about data leaks, as the cards contained transaction records of the owners. The police are not authorised to retrieve or process the data contained on cards and must hand them to Octopus for further processing.
Cheng said this procedure was appropriate.
'Legally speaking, the ownership of the smart card belongs to the Octopus company as the card users pay the deposit to the company for the right to use the cards - rather than owning the cards,' he said.
About 95 per cent of Hongkongers use Octopus cards
The number of smart cards the company has issued: 21m