The House has just passed the “Emergency Economic Stabilization Act” and you may want to flip to page 270 to read Section 301, which is called the Extension and Modification of Research Credit. This little chunk of legislative verbiage renews a federal tax credit for corporate R&D, which had expired last year. Now, though, the credit is revived, because it’s retroactive to this past January 1.

Why does this matter? Well, had the credit been in place this year, corporate earnings would have benefited from lower tax rates. Of course, we are now in this year’s fourth quarter, so the retroactive credit can give drug and device makers a nice earnings boost. And they stand to get a lift next year as well, since the credit was extended through December 31, 2009.

Of course, the gain will vary by company, depending upon whether this or that drug or device maker believed the credit would have been renewed or not. The credit was actually subject to periodic renewals, so this may explain why investors are likely to hear changes in financial forecasts on upcoming earnings calls (Dow Jones has more on this, by the way).

“It will be a substantial reduction to the effective tax rate of these companies, particularly in the life sciences industry where they’re really driven by R&D spend,” Thomas Hogan, a partner in charge of global R&D tax services at Deloitte, tells the Dow.