Canon PIXMA TS6420a will not print or scan two-sided

The checks in more detail

Start with the setting. In the print window of your program, open the printer's properties or preferences and find the page setup or the print quality tab, then choose Duplex Printing, or Print on both sides, and select Auto. On a Mac, choose Two-sided in the print dialog under Layout. If the option is grayed out, the driver may be a generic one; install the Canon driver or use the Canon PRINT app, and check that the paper source is set to the cassette and the paper size and type are supported for two-sided printing.

Plain paper in common sizes works best; envelopes, photo paper and thick or labeled stock may not be supported for automatic two-sided printing. If the second side prints upside down or in the wrong order, change the binding setting between long-edge and short-edge binding, which decides whether the back is flipped along the long or the short edge: long-edge suits documents that turn like a book, short-edge suits those that flip like a notepad.

If pages smudge, give the ink time to dry by choosing a longer drying time or by printing fewer pages at a time, use paper made for inkjets and avoid heavy graphics on the first side. If a jam occurs, clear the paper and check that the cassette is loaded flat, with the guides snug. If the printer pulls two sheets, fan the paper and keep it dry. As a last measure, print the odd pages, flip the stack and print the even pages manually. Contact Canon support with the model number if automatic two-sided printing fails with plain paper and the right setting.