I'm working on a show at Warner Bros right now, and was told that WB doesn't allow for rate to run through Loanout ever, so I've been doing similar to what everyone here is suggesting: rate through timecard, rentals through the corporation.
However, I did email Barbara Jerome regarding IATSE's policy regarding the use of loanouts for rate as well as rental, just trying to understand why WB would have the police they do. The accounting dept of my show indicated it was a union policy not to allow loanout, but when I emailed Barbara, I got this response:
It is not a union rule. It is a WB policy. We have no issue with you being compensated through your loanout as long as you submit a time card and get your benefits via WB.
Perhaps I am extrapolating too much from that, and I've done a few promos and music videos that were IA through my corporation (one was entirely payroll, the other was payroll for rate and invoiced for rental), so I need to find out if everything worked as I imagined. However, I figured that indicating I was using the loanout for the hours worked, and on the time card I had to give my social security number AND the Federal tax number, I figured that the social was used to report benefits paid to the union on my behalf and the Federal Tax number was for reporting the income.
I need to call around tomorrow to verify that the hours from those jobs were reported on my benefits, but that's how I figured it worked. SSN for the benefits to be paid, and the Federal Tax number for all income paid to my corp.
In my research regarding Workman's Comp (at least in California), most workman's comp (and workman's comp insurance) passes through the loanout to the individual working on the production. So, if I am working for a production, I am covered by their workman's comp policies as a pass through to me, individually, not the loanout corp. SOME workman's comp policies specifically do NOT pass through (perhaps they're cheaper? or have been used for fraud before?). I've worked for one company that specifically cited their workman's comp as a reason I couldn't use my corp.
Anyway, considering I'm not an accountant and still getting my feet wet with the use of my corporation, I'm still learning, so don't bet the farm on my advice. However, I took Barbara's response to mean the unions have no problems with us using loanouts for the rate, so long as the benefits contributions are still made in our name (hence why your social security number should be on the timecards even when using the loanout). I've crossed out the W4 exemptions sheet on a few union gigs, ran it all through my corp and nobody seemed to have any issue. Of course, I'll be irked if my benefit hours aren't there... will report back when I know more.