For those of you who need to unroot your Galaxy Note 4, perhaps because you need to return your phone for warranty, need to get out of a nasty bootloop, or simply tired of using custom ROMs and want to run stock, you can do so easily by re-installing the stock firmware.
Now, unrooting with stock firmware does not erase anything if you are coming from stock ROM or firmware, it will simply update you to the latest stock firmware you flash. However, if coming from custom ROM, you may need to do a factory reset. Doing a factory reset in stock recovery (after unrooting) WILL ERASE EVERYTHING on your phone. You may have to do that so if you are coming from custom ROM, BACKUP EVERYTHING on your phone before following the guide.
Step 1. Check the model number of your Note 4 in Settings->About device. Min says “SM-N910F” so I will need a stock firmware with model number SM-N910F.
Step 2. Power off your Note 4 then hold down Volume Up, Center Home, and Power buttons together for about 5 seconds until you see a warning screen like shown below:
Step 3. Hit Volume Up button to enter Download Mode and connect a micro-USB cable from your Note 4 to your computer.