Per the IRS website....
Exceptions The following is a list of transactions that are not reportable; however, you may choose to report them. If you do, you are subject to the rules in these instructions. 1. Sale or exchange of a residence (including stock in a cooperative housing corporation) for $250,000 or less if you received an acceptable written assurance (certification) from the seller that such residence is the principal residence (within the meaning of section 121) of the seller and the full amount of the gain on such sale is excludable from gross income under section 121. If the certification includes an assurance that the seller is married, the preceding sentence shall be applied by substituting “$500,000” for “$250,000.” If there are joint sellers, you must obtain a certification from each seller (whether married or not) or file Form 1099-S for any seller who does not make the certification. Also, the seller must include in the certification that there has been no period of nonqualified use (as that term is defined in section 121(b)(5)(C)) after December 31, 2008, and as required by section 6045(e)(5)(A)(iii), that the full amount of the gain from the sale is excludable under section 121. The certification must be signed by each seller under penalties of perjury. A sample certification format can be found in Rev. Proc.
