Generally there is not much to worry about if you do not owe taxes, because interest and penalties are based on tax due. So if zero tax they'll be zero penalties or interest payable.
However the form TDF 90-22.1 has an automatic penalty of $10,000 for late filing (it is due by 30 June each year) so if you have to file this form because you have foreign (eg UK) bank or security accounts with balances that exceeded $10,000 at any time in the year you'll need to try to file these on time.
