We toyed with this idea of mom not claiming the kids last year (first year we had to deal with this), but in the end, she wanted to claim them so as to not jeopardize any of their social security benefits. I don't know anything about whether she'd lose benefits if she's not claiming them as her dependents, but we went ahead and put them on her return and paid the tax on the boys' returns. Last year, the tax to the boys was about half, but this year, with the new rates I guess, the amount is $1200 per kid. I'm just trying to see if there is something that I'm missing. I'll work out the support worksheet though and go from there.