In an era of tightening credit, a credit expert is reminding Canadians to check with credit-rating agencies to make sure their files are mistake-free and up to date.

"Over 80 per cent of Canadians have never checked their score, and they should," Kevin Leonard, an associate professor at the University of Toronto, told the CBC.

Leonard is an expert in statistics and information theory for business and for several years worked as a consultant with Fair Isaac Corp., the company that developed the number-crunching models for credit-rating companies.

"Some of the information they use to assess your credit rating could be wrong, and that could cost you a lot of money," he said.

The country's two largest agencies, Equifax Canada and TransUnion Canada, keep files assessing the credit-worthiness of more than 20 million consumers.

That includes information about every loan taken out in the last six years — whether payments are regularly made on time, how much is owed, what the credit limit is on each account, and a list of authorized credit granters who have accessed a file.

A company that is thinking of granting a person credit or providing a service that involves receiving something before it's paid for (like phone service or a rental apartment) can get a copy of the person's credit report.

18 per cent of those who checked found inaccuracies

A 2005 study by the Public Interest Advocacy Centre showed that only 4.2 million Canadians, of 17 per cent of the population, had checked their credit ratings in the previous three years.

Of those Canadians, 18 per cent uncovered inaccuracies. The vast majority of those people asked the agencies to correct the errors but it took, on average, four hours to get a problem-free credit report.

Mistakes in credit ratings can cost consumers higher interest payments, especially on big-ticket items such as mortgages.

"It has a large impact on their bottom line — what [consumers] pay over the life of a mortgage, car loan, line of credit, you name it," said Leonard.

Credit rating agencies publicly acknowledge there can be mistakes, but say they are obligated by law to do their best to ensure the accuracy of the information. They also offer places on their websites to report inaccurate information.

Consumers can get their ratings mailed to them for free — either by contacting the agencies directly, or by following the links on their websites offering a free copy.