HP Instant Ink is an ink cartridge replacement service. To participate, enroll your HP Instant Ink eligible printer in an Instant Ink plan. The plan charges a fee based on the number of pages you print/copy each month. The printer sends ink level information to HP, and when the printer runs low on ink, replacement ink cartridges are shipped to you. You do not need to purchase replacement ink cartridges from retail stores when you are enrolled in HP Instant Ink.