rbynaker
Level 13

I think you're making broad generalizations when you really just need to go through the worksheet and do the math.  See Pub 501 page 15:

https://www.irs.gov/pub/irs-pdf/p501.pdf

Some items are "household" support and will be split among the occupants but others are directly related to each child.  You may have a situation where one or two children provide more than 50% of their own support and one or two do not.  It just depends on the numbers involved.

The bigger problem (and the reason I stay away from these cases) is that you might not be able to get the data needed to complete the worksheet.  How much was spent on Johnny's clothing vs. Sally's clothing?  I doubt anyone knows.  But every case is going to be different, have the client give their best estimate and see where the numbers lead you.  If you're in a situation where being off by $2K on clothing won't change the conclusion then you don't sweat the small stuff.  On the other hand, if Sally may have provided 49-51% of her own support then the details matter a whole lot more.