If you think you may be getting an RC62 slip, you can check with CRA using "My Account" (if you are signed up for it), or call General Enquiries 1-800-959-8281. As stated above the majority of people WILL NOT receive an RC62 for the 2017 tax year, the slip will only be issued to those who received "back pay" for UCCB benefits prior to July 2016, or if you made a repayment.
