Does the NEC require a typed panel directory?

No. NEC 408.4(A) requires circuits to be legibly identified with a clear, evident, and specific purpose. It does not specify a printing method, so neat handwriting is acceptable.

Why is labeling a circuit with someone's name a violation?

NEC 408.4(A) prohibits identification that depends on transient conditions of occupancy. Occupants change, so the room or the load must be named instead of the person.

Can you label a panel directory with a permanent marker?

Q: How durable does a panel label have to be?

NEC 110.21(B) requires field applied markings to be permanently affixed and to have sufficient durability to withstand the environment involved, which matters most in damp, outdoor, or sunlit locations.

There is no section in the 2023 NEC that prohibits handwriting a residential circuit directory. What the code actually requires is that the identification be legible, specific, and durable. A permanent marker on the printed directory card satisfies all three when it is done neatly. A ballpoint pen on a strip of masking tape usually does not.

What 408.4(A) requires

Section 408.4(A) of the 2023 NEC requires every circuit and circuit modification to be legibly identified as to its clear, evident, and specific purpose or use. The identification must include sufficient detail to distinguish it from all other circuits, and where the circuit identification is not evident, it must be included in a circuit directory located on the face or inside of the panel door for a panelboard, or at each switch or circuit breaker in a switchboard or switchgear. No circuit may be identified in a manner that depends on transient conditions of occupancy, which is why "Bob's room" is a violation and "Bedroom 2 receptacles" is not.

Nothing in 408.4(A) says printed, typed, engraved, or machine made. The word the code uses is legibly. That is the standard your handwriting has to meet.

Where 110.21(B) comes in

Section 110.21(B) governs field applied hazard markings and, more generally, sets the durability bar for labels required by the code. It requires the label to be permanently affixed and to have sufficient durability to withstand the environment involved. Inside a dry, indoor loadcenter door, a solvent based permanent marker on the manufacturer directory card easily meets that. In a garage or an outdoor NEMA 3R enclosure where condensation and sunlight are in play, a water based marker will fade and smear, and then you are out of compliance the day the inspector reads it.

What actually gets red tagged

The common failures are not the writing instrument. They are vague descriptions such as "lights" or "misc," circuits identified by the occupant's name, blank spaces next to energized breakers, a directory that was never updated after a remodel, and spares that are still labeled with the old load. Section 408.4(A) also requires that where a circuit is modified, the directory be updated to match. If you add a circuit, you own the directory.

Two other labels people forget

Section 408.4(B) requires a panelboard or switchboard supplied by a feeder in other than one and two family dwellings to be marked to indicate the device or equipment where the power supply originates. Section 230.85 in the 2023 edition requires an emergency disconnect at one and two family dwellings with specific field applied markings, and those markings also fall under the 110.21(B) durability rule.

Field takeaway

Write it in permanent marker if you want, but write it neatly, write it specifically, use the manufacturer directory card, and update it when you touch the panel. Legible and specific is the code test. The pen is not.