Fleet managers are being urged to check photocard driving licences as around 90,000 are due for renewal this year.
Drivers must change the photograph on their licence every 10 years or they could be fined up to £1,000.
As the first photocard licences were issued in July 1998, thousands need to be updated.
But many drivers are not aware that their licence is due for renewal.
A survey of nearly 2,000 drivers found that 45% of photocard licence holders do not know their licence’s expiry date.
Drivers should receive a reminder in the post two months before the renewal date, but this is reliant on people telling the DVLA when they change their address.
Failure to notify the DVLA of a new address can also result in a £1,000 fine.
“There is clearly a risk that some drivers will not be aware that their renewal date has passed.
"These drivers will unwittingly find themselves driving on outdated licences,” said Mark Sinclair, director of Alphabet, which carried out the survey.
“It is an essential part of companies’ duty of care to make sure that every employee who drives on business holds a valid, up-to-date driving licence.”
Mr Sinclair added that by the end of next year, around 150,000 photocard licences will be due for renewal every month.
It costs £17.50 to renew a photocard licence after 10 years.