How the Fee for Not Having Coverage Works
If you aren't exempt from the shared responsibility fee (fee for not having coverage) and choose not to get health insurance (known as minimum essential coverage) in 2014 you will owe a per-month fee for every month you go without coverage.
The only way for the IRS to collect the fee for not having health insurance is to withhold the money you would get back after filing your federal income tax returns. The IRS cannot enforce the Individual Shared Responsibility provision with jail time, liens, or any other typical methods of collection.
Please keep in mind that about 75% of Americans got a refund in 2012 and many who aren't owed a refund will be exempt from the tax anyway.