I am adding a 30 amp sub panel - the problem I have is the neutral bus is full what are my options?

Best answer - If panel can accept, add an additional bus on the other side and bond the two together.

Least desirable answer - split bolt the neutral to one of the existing. Under no circumstances should you place multiple wires under one terminal.

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The neutral wire for the sub panel will only be a #10 conductor. Neutral wires can be doubled up under a single screw in the neutral bus. Turn the main breaker off to do this installation. Double up two #14 neutrals to make room for the #10 neutral wire. There is no code rule as to how many wires can be installed under a terminal on the neutral bus. There is a code rule though about not doubling up circuit feeders under one breaker terminal.