The Internal Revenue Service has issued new rules taking aim at the transfer pricing arrangements corporations often use to develop new technologies—a move that piles on more concern about valuing intangible assets and disclosing tax uncertainties.

Issued in the last days of 2008, the rules went into effect with the start of this year. Their final language largely follows the plan first proposed by the IRS in 2005, which has been razzed by corporate tax advocates ever since. Still, the long-simmering battle is not necessarily over. The IRS remains open to comment through April 6 and has scheduled a hearing on the measure for April 21.