How to Fix the Dreaded 'Waste Tank Filled' Error Message for Your Canon Printer

With the printer power turned off, while pressing the Resume/Cancel button, press and hold the Power button. (DO NOT release the buttons. The LED lights in green to indicate that a function is selectable.)
While holding the Power button, release the Resume/Cancel button. (DO NOT release the Power button.)
While holding the Power button, press the Resume/Cancel button 2 times, and then release both the Power and Resume/Cancel buttons. (Each time the Resume/Cancel button is pressed, the LED lights alternately in orange and green, starting with orange.)
When the LED lights in green, press the Resume/Cancel button 4 times - Waste ink counter resetting. (Each time the Resume/Cancel button is pressed, the LED lights alternately in orange and green, starting with orange.)
After the function (menu) is selected, press the Power button. The LED lights in green, and the selected function is performed. (When the operation completes, the printer returns to the menu selection mode automatically.)
If the printer is now off, the process is finished, otherwise press the Power button one more time to set the function and to shut down the printer.