What are the NEC requirements on the use of the white wire in an NM assembly for an ungrounded conductor and when did this first become a requirement?
Goes back at least 30 years, white or natural gray is to be used for grounded conductor only. Otherwise the conductor needs to be re-identified at each termination or where visible.
Current NEC 2020 requirement for NM:
According to the 2011 NEC: the white NM cable if being used for an ungrounded feeder: It has to be permanently identified at all visible ends. The ID must encircle the feeder and be marked with any color except for white, grey or green.
The white conductor has been permitted as an ungrounded conductor in a cable assembly for at least 100 years. A 2-wire switch loop being the most common use of the white conductor as the hot leg down to the switch. This was easily identifiable in the lighting outlet box because the white conductor going down to the switch was connected to the hot leg at the box.
The 1999 NEC had a considerable re-write of Article 200 (Use and Identification of Grounded Conductors) which required the white conductor in a cable assembly to be re-identified when used as an ungrounded conductor.
You’re welcome. It’s common in older homes to see the white spliced to the hot leg at the ceiling lighting outlet without any re-identification. An electrician would know that the white is being used as the hot leg to feed the switch when there is only a two wire cable.
Also common is seeing a 2-wire cable being used for a 240 volt circuit where the white conductor is connected to one pole of the 2-pole circuit breaker. In older installations this conductor will not be re-identified at the circuit breaker and although its use as a hot conductor is obvious the NEC wants to be even more clear so they now require the re-identification.
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Electricity 101: White of the switched leg to the black of the feed.
You’re correct. Electricians did this for about 75 years before the NEC decided to dumb it down for handymen, homeowners, and DIY’ers. The prevalent opinion amongst electricians is that if you don’t know why the white and black conductors are spliced together then you should not be touching it.
Was re-identifying not required before 1999?
I believe that the 1999 NEC added the re-identification requirement. Prior to that we never re-identified the white conductor. If you pulled out an existing SP wall switch often there were only two conductors landed on the switch one black and one white. The white was hot.
What code cycle?
That’s from 1981
Are any home inspector’s actually taking down light fixtures to check to see if the wires are marked to code? 
How many angels can dance on a GIF? 
I think it’s something to do with the panels most home inspectors open and check unless they are from Ohio. You’re not from Ohio, are you Joe?
Prior to the 1999 NEC a white conductor in a raceway could be re-identified as an ungrounded conductor. The 1999 removed that completely and limited re-identification to cable assembly’s only.
Are you saying prior to NEC 1999, NEC article 200-7 did not apply to NM or other cable assemblies? where does NEC 1981 state this?
1981 NEC:
Look at 200-7 Exception No. 2 which states that the white conductor within a cable does not require re-identification.
I have, but it refers to the switch loops only just like it does in NEC 2020. What about:
Were you referring specifically to the switch loops only? As home inspectors, we rarely ever open outlets (rarely a faceplate is missing and we can see inside). Panels is where we normally see white used as ungrounded and black as grounded.
NEC 1981 200-7 exception #2:
NEC 2020:
I don’t believe that it was only switch loops but it certainly could have been being that the new language was added in the 1999 NEC which was over 30 years ago. I’ll have to do some digging around possibly in the 1999 ROP which had the rewrite of 200.7.
You’re correct that it is almost certain that if the white conductor is not re-identified that it will be found by the HI at the panel. There must be a hundred photos on here that show just that.
This is an excerpt from the Ohio SOP
(T) A licensee shall inspect a property’s readily accessible components of the electrical system during a home inspection and report in the home inspection report the licensee’s findings related to all of the following:
(1) Service drop;
(2) Service entrance conductors, cables and raceways;
(3) Service equipment and main disconnects;
(4) Service grounding;
(5) Interior parts or components of a service panels and subpanels;