Hundreds of thousands of drivers in B.C. will be getting insurance premium refunds, after public auto insurance provider ICBC under- or overcharged 441,000 customers over the last six years.

A news release from the insurance corporation said letters will be sent to all customers who either overpaid or underpaid for optional additional coverage.

"We sincerely apologize for any inconvenience this has caused our valued customers," spokesperson Adam Grossman said in the statement.

Drivers who overpaid will be reimbursed, ICBC said, with the average cheque amounting to about $18 for each year of the error.

Drivers who underpaid will not have to repay any cash. ICBC said the issue has cost it more than $100 million in either lost revenue or reimbursements.

ICBC said the wrong premiums were charged because wrong vehicle descriptions were applied, but new software will prevent the issue in future.

"This is a very complex issue, and ICBC is committed to ensuring there is accurate information on vehicle descriptions for all customers prior to launching a new computer system for its insurance business," the news release said.

The new technology automatically identifies the vehicle's description using the vehicle identification number, or VIN, provided by the automobile's manufacturer.

ICBC urged anyone with additional information to provide or questions about their letter to call 604-904-8211 in the Lower Mainland or 1-866-506-0030 toll-free within B.C.

With files from The Canadian Press