Is it safe to use non-HP or refilled ink cartridges in the HP DeskJet 3720?
Using a non-HP or refilled cartridge does not automatically void the printer warranty or any HP support contract. However, if printer failure or damage is attributable to the use of a non-HP, refilled, or expired ink cartridge, HP will charge its standard time and materials charges to service the printer for that failure or damage.
From the official HP Deskjet 3720 All-in-One Printer manual, page 3
Have a follow-up question?
Answers from the official manual.
Common questions