The Canada Revenue Agency is warning Canadians about a mail scam involving bogus letters that ask for personal information to enable the agency to update its records.

The letters are fraudulently identified as being from the agency.

Each one claims there is "insufficient information" from the individual's tax return, and to receive "claims," the person is required to complete an attached form that asks for such details as passport and bank account information. The form is to be in writing and returned by fax or e-mail.

Ron Quinn, spokesperson for the Canada Revenue Agency in Edmonton, said the letters are not from the agency.

"It looks authentic to some degree, but we would never ask for some of the things that are in the letter. We wouldn't ask for such things as your passport, your bank account, your mother's maiden name and so on. We just don't operate in that way."

Quinn said the agency has already notified police and posted a warning on its website. He urged anyone who has received the letter to call police as well.

On its website, the agency has attached a copy of the letter, which includes what appears to be on CRA letterhead and includes an illegible signature.

"All taxpayers should be vigilant when divulging any confidential information to third parties. The CRA has well established practices to protect the confidentiality of taxpayers' information," the agency's website advises.