It is based on Household Income, which is a term specific to ACA.
Income Criteria
To be eligible for the premium tax credit, your household income must
be at least 100 – but no more than 400 – percent of the federal poverty
line for your family size, although there are two exceptions for
individuals with household income below 100 percent of the applicable
federal poverty line. Remember that simply meeting the income
requirements does not mean you’re eligible for the premium tax credit.
You must also meet the other eligibility criteria.
For information about the two exceptions for individuals with
household income below 100 percent of the federal poverty line, see the instructions to Form 8962.
Here are four things to remember about how your income affects your premium tax credit:
- The amount of the premium tax credit is based on a sliding
scale, with greater credit amounts available to those with lower
incomes.
- If the advance credit payments made on your behalf are more than
the allowed premium tax credit, you will have to repay some or all the
excess. If your household income is 400 percent or more of the federal
poverty line for your family size, you will have to repay all of your
excess advance credit payments.
- If your projected household income is close to the 400 percent
upper limit, be sure to carefully consider the amount of advance credit
payments you choose to have paid on your behalf.
- If your household income on your tax return is more than 400
percent of the federal poverty line for your family size, you are not
allowed a premium tax credit and will have to repay all of the advance
credit payments made on behalf of you and your tax family members.
For purposes of claiming the premium tax credit for 2017, the
following table outlines household income that is at least 100 percent
but no more than 400 percent of the federal poverty line.
8. What is household income?
For purposes of the premium tax credit, your household income is your
modified adjusted gross income plus that of every other member of your
family (see question 6) who is required to file a federal income tax
return. Modified adjusted gross income is the adjusted gross income on
your federal income tax return plus any excluded foreign income,
nontaxable Social Security benefits (including tier 1 railroad
retirement benefits), and tax-exempt interest received or accrued during
the taxable year. It does not include Supplemental Security Income
(SSI).
https://www.irs.gov/affordable-care-act/individuals-and-families/questions-and-answers-on-the-premiu...
