"For first-time homebuyers this year, this special feature can put money in their pockets right now rather than waiting another year to claim the tax credit," says IRS Commissioner Doug Shulman in announcing the filing year choice.

If you don't need the money immediately, however, it might be better to wait and take the credit on your 2009 return.

The choice is yours. You can claim the credit now or claim it later, based on which filing year provides you with the best tax result. So run the numbers first before making a filing year choice.

And if your first-home purchase occurs after the 2008 filing deadline, which could be as late as Oct. 15 if you get an extension, you can file an amended return to make the claim.

2008 purchasers locked in

Buyers of first homes between April 9, 2008, and Dec. 31, 2008, can claim the credit, but only under the original terms.

This means they are allowed a maximum tax break of only $7,500 or 10 percent of their home's purchase price.

And any credit amount must be paid back over 15 years, starting with the 2010 return.

Credit e-filing on hold

Form 5405, which taxpayers must use to take the first-time home purchase tax break, has been revised to reflect the new purchase dates and $8,000 credit amount. However, it's not yet been formatted and approved by the IRS for e-filing.

"All of the tax software industry is waiting for the IRS to release a time frame around which e-filing will be accepted," says Denise Sposato, director of communications and communities for H&R Block. "You can download the form and go into one of our offices and manually file it. You would have to mail it in, and there is some delay in that."

Intuit's TurboTax software packages are in the same boat. "We are actually pushing updates out to TurboTax, but the forms are still only printable," says Julie Miller, director of corporate communications for Intuit. "It's not any different from prior years when we had electronic forms that were late because of congressional changes."