Taxpayers are able to sign up for "My Account" on the CRA website...as well as allowing the taxpayer to see the status of tax returns and check for tax slips and other information, this also allows taxpayers to request adjustments to returns already filed, and to do so right on the CRA website. Especially if it is an adjustment using information that CRA already has, the processing time for this can be much quicker than submitting a request by mail.
http://www.cra-arc.gc.ca/myaccount/
