@Raj1 , while you are supposed to file the FBAR form in time and willful disregard of the requirement is punished by excessive fines , it is rarely used. The idea is to get compliance from taxpayers. If you missed only once , there is no consequence but habitual dis-regard is invitation to shock the taxpayer into compliance. I do not believe you need an explanatory note if this is first time but ....
Does that answer the question ?
pk