A household, for purposes of determining eligibility for premium tax credits, includes any individuals whom you list on the federal tax form. That includes yourself, your spouse, and dependents. Dependents include children who meet certain requirements:
Other adults who can count as dependents include relatives, in-laws or full-time members of your household who:
A household can include individuals even if they are ineligible for tax credits (for example, individuals who are not lawfully present). Your household size can change during a year due to family changes, including the birth or adoption of a child, a child moving out of the house, and divorce or legal separation. When such changes take place you should report them to the Marketplace as they may affect your eligibility for subsidies. Family changes also can trigger a special enrollment opportunity when you can change health plans, even outside of the regular Open Enrollment period.
Note that the definition of household for determining eligibility for premium tax credits sometimes differs from the definition of household for determining Medicaid eligibility. Ask your Marketplace for more information about who should be counted in your household.