Health Insurance

If you don't have health insurance in 2015, you'll pay the higher of these two amounts:
2% of your yearly household income. (Only the amount of income above the tax filing threshold, about $10,000 for an individual, is used to calculate the penalty.) The maximum penalty is the national average premium for a bronze plan.
$325 per person for the year ($162.50 per child under 18). The maximum penalty per family using this method is $975.
If you didn't have coverage in 2014, you'll pay the higher of these two amounts when you file your 2014 federal tax return:
1% of your yearly household income. (Only the amount of income above the tax filing threshold, about $10,000 for an individual, is used to calculate the penalty.) The maximum penalty is the national average premium for a bronze plan.
$95 per person for the year ($47.50 per child under 18). The maximum penalty per family using this method is $285.

The after 2015

The penalty increases every year. In 2016 it's 2.5% of income or $695 per person. After that it's adjusted for inflation.

How you pay the fee

You'll pay the fee on the federal income tax return you file for the year you don't have coverage. Most people will file their 2014 returns in early 2015 and their 2015 returns in early 2016