The serial number for your Oculus headset can be found on the headset strap, the controllers and the original Oculus packaging.
To locate the serial number for your headset:
Gently pull the right side strap arm back away from the lenses to expose the 14 character alphanumeric serial number.
If the headset straps are on a looser setting, the serial number may already be exposed without having to pull the strap.
To locate the serial number for the controllers:
Remove the battery cover from the controller by sliding it level, but away from the controller.
The serial number will be on the inside of the controller underneath the battery.
To locate the serial number for the Oculus for Business package:
Look for a small, white sticker marked with a barcode on the outside of the Oculus for Business box.
Under the barcode, find S/N followed by the 14 character alphanumeric serial number.