Shared Neutral

Brain fart.....Are shared neutrals allowed? What would you write up for the corrective action?
I should know this, but I've encountered several problems today and I'm too frustrated with the other problems for writing this one up.
Thanks!

Chad:

Yes, for a multiwire circuit a neutral is shared. Each 120 volt must originate on bus a and b for the multiwire circuit so only the difference returns on the neutral.

http://ecmweb.com/content/multiwire-branch-circuits-can-be-dangerous

Chad D wrote:Brain fart.....Are shared neutrals allowed? What would you write up for the corrective action?
I should know this, but I've encountered several problems today and I'm too frustrated with the other problems for writing this one up.
Thanks!

Are you referring to double lugging neutrals?

Thanks Mike!
I always appreciate your help.

Roy,
I was not referring to double tapping (lugging). Inside the main panel I had about half as many grounds and neutrals that should have been there. Upon further review, half of the breakers had black wires and the other half have red wires. So that told me there were many shared neutrals. I'm sure I've seen this before, but it's not common that I see it. I have never done that when I have wired a panel.

New NEC code mandates shared neutral breakers have handle ties on them