You may see a smudge on the back of the printout when excessive ink remains on the paper guide. The paper guide is the dark plastic strip inside the printer. In this case, you can solve the problem by using the Paper Guide Cleaning utility in your printer driver.
Refer to the appropriate section below.
Note:
Repeat the procedure until the inside of the printer is cleaned.
Using the Paper Guide Cleaning utility for Windows
Follow the steps below to clean the paper guide using the Paper Guide Cleaning utility.
Make sure that no error light is flashing or on.
Make sure A4 size plain paper is loaded in the sheet feeder.
Open the printer driver, click the Maintenance tab, then click the Paper Guide Cleaning button.