Time is running out on a one-time tax deal for investors who want to transfer, or "convert," money from a taxable individual retirement account to a Roth IRA.

Thanks to a law that took effect Jan. 1, all taxpayers are now permitted to convert a regular IRA to a Roth. Before then, conversions weren't allowed for those earning more than $100,000. (Roth IRA contributions, in contrast, remain off-limits for individuals with modified adjusted gross income of $120,000 or more and married couples with income of $176,000 or more.)

That means anyone willing to pay the income taxes due upon converting can move retirement savings into a Roth, where the money can grow tax-free.

To make that more palatable, Uncle Sam is offering a special deal that expires on Dec. 31. Those who convert in 2010 can choose to report the income on their 2010 tax returns or they can spread the income equally across their 2011 and 2012 returns.

Courtesy of WSJ.com

Here's a Roth Conversion Calculator