Currently I'm paying the mortgage on our marital home and my ex is living there and plans to buy me out. The plan is to give her 3 years to refinance (or she has to sell, since I'm on the mortgage and deed).

Because of that arrangement, for temporary support what I've been paying her has been:

child_support + alimony - mortgage_payment

This has worked well as it's a single payment from me to her, and I don't have to rely on her paying me back the difference (mortgage payment is higher than alimony component of the support payment).

My question is, if we both agree and put it in a legally binding document, can this sort of formula continue? Or does the state of California require that the CS payment be paid through the state?

If child support must go through the state, do I have to pay her the full alimony amount, then have her pay me the full mortgage amount? Or could I just not pay her anything (other than the automatic CS payment) and then require she reimburse me for the mortgage_payment - alimony difference each month?