2 Single Member Business', same owner... can either business pay the ER Cont?

[Basically]

This client owns a business and is going to open another business (both in the financial arena).  I can use the same plan document for both plans... using the joinder agreement option... it's a control group.

IF the client wants to max out the ER, does it matter which business ponies up the money?  OR... if the client earns $100K from company A then company A needs to pony up $25K (and so on with Company B)

Thanks

[CuseFan]

This has come up before in this forum. My understanding is that if a consolidated return is filed for the control group then the contribution dollars can come from either entity in whatever proportions. If each business filed its own tax return then deduction is based on contributions for each one's respective employees and compensation.

Here, you have two disregarded entities that just pass through income to the owner so you certainly have a "consolidated" return - one tax return for the owner, correct? 

I'm not an accountant and this is not advice, client should confirm with qualified tax accountant.