First of all, the previous home must have been occupied as the buyer’s principal residence for at least five consecutive years out of the past eight years. Two examples: (1) Suppose that during the past eight years you occupied the property for three years, then rented it out for two years (perhaps because of a job transfer or temporary assignment), and then occupied it again for three years up until now. Even though you had occupied the property as your principal residence for six of the past eight years, you would not be eligible because you had not occupied it for five consecutive years. (I’m not saying this makes sense; I’m just reporting on the requirements.) (2) Suppose you bought a home eight (or more) years ago, you occupied it as a principal residence until two years ago when you sold it. Would you qualify? Yes, because you had occupied it as a principal residence for at least five consecutive years of the past eight.
There are important issues of timing as well. You must have purchased (that is closed on) the replacement home sometime after 11/6/2009 and before 4/30/2010. With one exception: the new home will also qualify if you had entered into a binding contract no later than April 30, 2010 and you closed no later than June 30, 2010.
The time the previous home sold doesn’t matter. Indeed, it doesn’t even have to be sold. You might, for example, keep it as a rental.
The tax credit is for 10% of the purchase price up to a maximum credit of $6,500 for joint filers and $3,250 for those filing separately. There is a full credit for singles whose income does not exceed $125,000 and for couples whose income is no more than $225,000. A phase-out applies to higher incomes up to $145,000 and $245,000 respectively.
The cost of the new home may not exceed $800,000.
The new home must be used as a principal residence for a three year period subsequent to closing, or else the credit must be repaid.
http://realtytimes.com/nl/nlpages134/1movedown.htm?open&ID=alansharpbarker