Cartridges can be refilled and then be reused without resetting and work perfectly. This means the reset chip that shows the toner or ink level is not replaced. THe cartridge will work perfectly but without showing the ink or toner level that is left inside the page and without showing the ESTIMATED NUMBER OF PAGES REMAINING: consider that this number is estimated because your cartridge or let me rather say printer does not know what type of pages you are still going to print in future: full A4 covering photos with a page coverage of 80% or more or just short letters with a coverage of 4 or 5%. 

So when you install the cartridge the printer will prompt the following message: cartridge used or Cartridge depleted – press ok to continue. So press OK to accept and continue printing!

In below Video you can see a short extract of me printing 1000 flyers for a friend with an officejet pro 8600 using HP 950XL – refilled (without new chips)