Business interests, including American Trucking Associations, American Truck Dealers and the Truck Renting and Leasing Association, are pressing Congress to extend certain tax provisions before the end of the year.

The 527 groups sent a letter to each member of Congress urging action during the lame duck session.

Among the provisions that are critical to business are the 50% bonus depreciation, research and development tax credits, business expensing and biodiesel and alternative fuel credits, the groups said.

These are among some 50 temporary tax provisions that expired last January. Unless Congress acts quickly, businesses won’t know how to file their taxes, the groups said.

“Failure to extend these provisions is a tax increase,” the letter says. “It will inject instability and uncertainty into the economy and weaken confidence in the employment marketplace.”

Congress has not made its intentions clear. The Senate Finance Committee has passed a bipartisan bill that would extend the provisions for two years, but the House still is at odds over which provisions should be extended and how long the extensions should last.