UPDATE 2-Boston Sci in U.S. tax fight tied to Guidant deal

* IRS says company owes at least $525 mln

* Boston Sci disagrees with IRS assessment

* Shares fall 2 percent (Adds analyst comment; updates share movement)

NEW YORK, Dec 21 (Reuters) - The U.S. government has informed Boston Scientific Corp (BSX.N) that it owes at least $525 million in taxes stemming from an acquisition, but the medical device company plans to dispute the finding.

Boston Scientific, whose shares fell 2 percent, received notices on Friday from the Internal Revenue Service, the company said in a U.S. securities filing on Tuesday.

The IRS claims the company owes the additional taxes based on an audit of the 2001, 2002, and 2003 tax years of Guidant Corp, Boston Scientific said.

Boston Scientific acquired Guidant in April 2006, a $27 billion deal that left the company saddled with debt.

The medical device company, which is seeking to reshape itself after years of struggles, needs every bit of capital it can muster, said Wedbush Securities analyst Phil Nalbone.

"It sounds like they might be adequately reserved" for the potential tax liability, Nalbone said. "The issue is that reserve ties up cash that would otherwise be used to make acquisitions and further the company's corporate development efforts. They very much need to make acquisitions to improve the growth outlook."

While Nalbone did not think the tax was weighing on the shares, he noted they had run up in recent weeks and, in his view, were "significantly overvalued at these levels."

The main tax issue relates to transfer pricing with technology license agreements between certain domestic and foreign subsidiaries of Guidant. The IRS asserts the tax liability is $525.1 million plus interest.

Boston Scientific said it disagreed with the methodologies applied by the IRS and that it would file a petition to the tax court to contest the assessment.

"The company believes that the IRS positions with regard to these matters are inconsistent with the applicable tax laws and the existing Treasury regulations and that the previously reported income tax for the years in question is appropriate," Boston Scientific said.

No payments on the assessment are required until a definitive resolution of the dispute, which could take several years, the company said.

Shares of Boston Scientific were down 2 percent at $7.66 in morning trading. (Reporting by Lewis Krauskopf, editing by Dave Zimmerman and Lisa Von Ahn)