I took this information directly from the California Association of Realtors Legal Q&A for you. It states the following:
You are not eligible for the tax credit if the taxpayer owned another main home at any time during the three years prior to the date of purchase. For a married couple filing a joint return, this requirement applies to both spouses. For example, if the taxpayer bought a home on Sept. 1, 2009, the taxpayer cannot take the credit for that home if he or she owned, or had an ownership interest in, another main home at any time from Sept. 2, 2006, through Sept. 1, 2009.
In conclusion and in answer to your question, I would take this to mean that you would need to file separate returns in order for you to receive any benefits from the tax credit. But only if you are to purchase a residence and close escrow before the Nov. 30th deadline and prove that you have not held an ownership interest in any home for the three years prior to the purchase.
You will need to calculate the difference between what you stand to gain by filing jointly with no tax credit vs. filing separately and receiving the tax credit. The limit is $4,000 for a married person filing a separate return.
Please confirm all this information with your tax advisor before making any decisions. Good luck to you! Congratulations on your engagement and pending wedding!
Diane Wheatley, Broker