On page 3 of the CA Schedule R you are given a choice of Single Sale Factor Formula or Three Factor Formula for the Apportionment Formula.  The instructions are totally vague as to which to use, but the tax result is better using the Three Factor Formula.  My client, an LLC member, had a one-time gig in CA, so no payroll or assets in CA, just sale of equipment to CA.  He went to the state several times, so I think nexus established.

Can anyone provide any guidance on which Apportionment Formula is required, or is it just optional?