If you do not pay off the entire balance by end of the financing period, you will be subject to interest charges going back to the date of your purchase. (rewardexpert.com)
This is the annual interest rate you will pay on purchases, if / when you can't pay off the entire balance by the payment due date outlined on your credit card statement. (ratehub.ca)
In a perfect world, you'd pay off your entire balance before the end of the promotional period (and accompanying low interest). (studentloanhero.com)