elmcitymaven,
When income is from employment, W-2 forms solve the problem of how much of the joint income comes from each partner. Similarly 1099s for income from separately held investments or interest bearing accounts.
If it is simpler for your mom to not separate her income from your dad's they jointly (not him alone) execute an I-864A and she reports the sum of their incomes on her I-864.
Yodrak
QUOTE(elmcitymaven @ May 5 2007, 10:50 AM)

Okay, I've googled on this topic and I *still* can't get my head around this. My mom is acting as joint sponsor for my husband as all my income has been earned outside of the US for quite a long time. What she wants to know is what figures to put down on Line 25, Federal income tax return information. My mom files her taxes jointly with my dad, so the figure for the adjusted gross income is the combined figure for both of them. Our question is this: does she put down the combined figure or does she try to tease out what her adjusted gross income might be separate from my dad's? She has said to me this might be difficult as the adjusted figure on the 1040 takes into account various deductions that they share -- would she just apply 50% of the total deduction in this case? Or does she use the unadjusted figure from her W-2?
If she is required to put down the combined figure, would my dad need to do an I-864A? He's happy to do so, but all of this is totally confusing. It doesn't help that I have lived pretty much my entire adult life outside of the States so I am fairly ignorant about W-2s and 1099s! If anyone can sort my brain out and give me some guidance on what figure she needs to put down we would both be in your debt!!