A payment (“penalty,” “fine,” “individual mandate”) you make when you file federal taxes if you don’t have health insurance that counts as qualifying health coverage for plan years 2018 and earlier. Starting with the 2019 plan year (for which you’ll file taxes in April 2020), the fee no longer applies.
Note: Some states have their own individual health insurance mandate, requiring you to have qualifying health coverage or be charged a fee when you file your state taxes for the 2019 plan year. If you live in a state that requires you to have health coverage and don’t have coverage (or an exemption):
Check with your state or tax preparer to find out if there is a fee for not having health coverage.