Why must I declare my son’s income on Form 8962? He is a dependent on my tax return. But he doesn’t contribute to our household expenses. When I include his income on Form 8962, the repayment limitation amount on Line 28 goes up from $1500 to $2500, and the tax I owe to the Feds goes up by almost $1400 on my 1040 tax return. So it is costing me double. I get less premium help on my wife’s health insurance plan because of my son’s income, plus I pay more Fed income tax because of his income. This seems to clearly be the law, but…
Claiming dependent's AGI is something to keep in mind when claiming credits on form 8962, a dependent can throw off household income and really mess with repayments and tax refunds. Knowing this sort of thing ahead of time can allow you to adjust tax credits in advance, or can allow you to not claim your dependent and have them get their own plan.
At this point the best suggestion is to look into other deductions you can take, and also if he isn't on your family plan then do consider not filing for him.
Learn more about filing taxes under the PPACA.