NEC 90.12: informational notes

What 90.12 Actually Says

NEC 90.12 is short, but it changes how you read the entire book. It states that informational notes and appendices are not enforceable requirements. They are explanatory material. The rules you must follow are in the numbered sections. Everything labeled "Informational Note" is reference, not regulation.

This matters because inspectors, apprentices, and even seasoned hands sometimes treat a note like code. It is not. If it is not in a numbered article or table, it does not carry the force of the standard. Know the line between the two before you argue a call in the field.

Section 90.12 was added to the 2023 NEC to make this crystal clear. Before that, the distinction lived in 90.5, which still defines mandatory, permissive, and explanatory rules. Read 90.5 and 90.12 together to understand what binds you and what does not.

Mandatory vs. Explanatory Language

Per NEC 90.5(A), mandatory rules use "shall" or "shall not." Those are the hard lines. Per 90.5(B), permissive rules use "shall be permitted" or "shall not be required." Those give you options. Per 90.5(C), explanatory material, which is what 90.12 covers, appears as informational notes printed in a different typeface.

When you are reading an article, scan for the word "shall" first. That tells you what has to happen. Then read the informational note if one follows. The note may reference another standard, give context, or point to a related article, but it will never add a requirement.

• Shall / shall not: mandatory, enforceable.
• Shall be permitted: optional, allowed method.
• Informational Note: explanation only, not enforceable.
• Informative Annex (A through whatever): reference material at the back of the book, also not enforceable unless specifically adopted.

Why Informational Notes Still Matter

Just because a note is not enforceable does not mean you should ignore it. Notes often point to the reason behind the rule, or to another standard that does carry weight in your jurisdiction. For example, the informational note at NEC 110.16 points to NFPA 70E for arc flash labeling details. NFPA 70E is a separate document, but OSHA enforces it, so you still need to comply.

Notes also reference adjacent code sections you might miss. An informational note after NEC 250.4 points to 250.50 through 250.106 for grounding electrode system details. Following those breadcrumbs keeps you out of trouble.

Field tip: if a note sends you to another NFPA standard or a UL listing, check whether your AHJ has adopted that standard. If they have, the reference becomes enforceable through the adoption, not through the note itself.

Informative Annexes

The back of the NEC contains Informative Annexes A through J (exact count varies by edition). These include conduit fill tables, ampacity examples, torque values, administration provisions, and cross references. Under 90.12, none of them are mandatory unless your local jurisdiction has specifically adopted them.

That said, Annex C conduit fill tables and Annex D calculation examples are the two most useful reference tools in the book for day to day work. Just do not cite an annex as the basis for a code violation. Cite the mandatory section it supports.

1. Annex A: product safety standards referenced in the code.
2. Annex B: application information for ampacity calculations.
3. Annex C: conduit and tubing fill tables.
4. Annex D: calculation examples.
5. Annex E: types of construction.
6. Annex F: critical operations power systems.
7. Annex I: torque tables.

How to Argue an Inspection Call

If an inspector fails you based on an informational note, push back politely and point to 90.12. Ask them which numbered section you violated. If they cannot cite one, the call does not stand on code alone. It may still stand on local amendments or AHJ discretion under 90.4, but you are entitled to a code citation.

Do not treat this as a gotcha. Inspectors are usually right, and notes usually track back to a real mandatory rule. Your job is to find that rule, understand it, and fix the install to meet it. Knowing 90.12 just keeps the conversation grounded in what the code actually requires.

Field tip: keep a copy of the NEC Handbook on the truck. The Handbook prints the code plus commentary in a different color. The commentary is not enforceable either, but it often explains the intent of a rule better than the note does.

Quick Reference for the Field

When you are flipping through the book on a job, use this sequence. Read the mandatory section first. Read any exceptions, because exceptions are enforceable and often save the install. Then read the informational notes for context and cross references. Then check Annex C or D if you need a table or calculation example.

Train your apprentices on this order too. New hands often latch onto the first piece of text they see, and if that happens to be a note, they walk onto the job with a wrong idea about what is required. Teach the hierarchy: article, section, exception, then note.

• Start with the numbered rule containing "shall."
• Read every exception listed under that rule.
• Use informational notes for context only.
• Use annexes for tables and examples, not as code authority.
• Check local amendments, since AHJs can promote notes or annexes to enforceable status.