1) If 2009 & older FBARs could not be filed in Jun 2010, due to knowing about it very late, but filed later (in 2010 or 2011), what will be penalty ?
a) if bank interest was declared on prior tax returns ?
b) if bank interest was not declared on prior tax returns ?
What will be penalty, in either case ?

2) If tax due less ($50), is it OK if only Form TD F 90-22.1 is filed for past years WITHOUT amending returns ? Can there be penalties in this case ?
OR old returns MUST be amended ?

Thanks.

As a general rule, I do not have clients amend returns to claim overseas interest if the resulting taxes is $50 or less. The IRS generally takes the attitude that such small additional taxes are de minimus (too small to be worth the effort to collect).

No, as to whether past-year Forms TD-F-99-22.1 should be filed, I have a call pending with the IRS to ask that very question. I suspect their answer will be that past year Forms TD-F-99-22.1 should be submitted, and if submitted late, they will waive any penalties, provided you remain compliance for future years.