Every time your printer runs a head cleaning routine, it takes ink from the cartridge, and forces it through the print head in order to try and clear any blockages. This ink ends up in the waste ink tank.
After you have printed a certain number of pages, the printer will automatically say that the waste ink tank is full, invariably though, it isn't anywhere close to being full.
You can reset this page counter by following the instructions below.
Please note, you do this at your own risk, if your waste tank is nearly full, you could soon have a lot of ink all over your desk!
1] Turn off the printer
2] Unplug the USB cable and power
3] Open the lid, press and hold the Power button
4] Reconnect the power cable
5] Close the lid and release the power button