The only way the IRS can collect the Obamacare “TAX” (not penalty) is to hold it out of your tax refund. If you make sure you aren’t due a refund, there is no way for them to collect it!
...At the moment...
The unpaid "Obamacare taxes" are cumulative and subject to interest and penalty assessments.
When total unpaid amounts reaches great enough levels you can expect "reforms" to the tax laws that will enable to IRS to collect those funds by seizure - and retroactively for past tax years.
Quite possibly those "reforms" will be enacted by Presidential decree at a press conference.
The elites running the present Government will attempt to do whatever is convenient for themselves and will not be restrained by Law or Constitution.
Plan accordingly.