Hello aosoriol:
You are quite correct in that if you are below the filing threshold balance ($100k if MFJ) for IRS Form 8938, then you don't need to file it in any instance . . . not with an original tax return or an amended tax return (I previously was unaware of the size of your accounts). However, as you will have noticed if you read the IRS.gov webpage at the link provided previously, the dollar reporting threshold for FinCen Form 114 is substantially lower than for Form 8938 (with a balance of just $10,000 on any day during the year).
Because of these differences, many taxpayers find that they have FinCen Form 114 disclosure obligation, but not an IRS Form 8938 filling obligation. This may include you as well.
Thank you for asking for this important clarification.
