For most taxpayers the rules for the exclusion are;
** Owned the home for at least two years.
** And lived in that home for at least two of the last five years. The two years living there doesn't have to be in sequence.
But there are some special considerations for military personnel and foreign service officers.
If you rented the home to others because you were on "qualified extended duty" with the military you can "suspend" that period of time in the capital gains calculation for "the last five years" timeframe. But, a suspension period can't be more than 10 years.
