Pfizer's attempt to escape the United States corporate tax rate by acquiring a British drug maker has set off a flurry of activity within other big companies across the country, at investment banks on Wall Street and in offices on Capitol Hill. Pfizer has offered to buy AstraZeneca for $106 billion. If the deal is successful, Pfizer would become an English company, reducing its tax bill at least $1 billion a year.

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The promise of such savings has many other big corporations seriously evaluating whether they, too, could reincorporate overseas. Walgreen is already under pressure from hedge fund investors that want it to move across the Atlantic. In New York, investment bankers and lawyers are urging clients to act quickly if they are serious about such a move, knowing that rules could change soon. In Washington, lawmakers have started to examine what legislation could be drafted to stop the outflow of tax dollars. Senator Carl Levin, Democrat of Michigan, on Thursday became the latest lawmaker to call for an end to so-called inversions, the deals through which United States companies acquire an overseas competitor and reincorporate abroad. He said he planned to introduce a bill to curb the practice. That could happen as early as next week, according to people briefed on the matter. More from the New York Times:

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End corporate taxation "It's become increasingly clear that a loophole in our tax laws allowing these inversions threatens to devastate federal tax receipts," he said in a statement. "We have to close that loophole." Any new laws are unlikely to arrive before more big companies move abroad. At a meeting in Paris last month, Walgreen investors, including the hedge funds Jana Partners, Corvex and Goldman Sachs Investment Partners, encouraged the company's management to consider an inversion, which would probably take place through an acquisition of Alliance Boots, a British drugstore chain in which Walgreen holds a 45 percent stake.

Walgreen's executives resisted the idea at first, concerned that the political cost would outweigh any tax savings.

But Pfizer's audacious proposal to acquire AstraZeneca opened the door for other companies to consider what was until recently viewed as a risky move. Now, Walgreen's management has begun to come around, people briefed on the matter said. "We are aware of all the inversions that are happening and certainly all of that is being investigated," Rick J. Hans, Walgreen's divisional vice president for investor relations and finance, said on a call with analysts just days after Pfizer announced its plans. "We're not averse to looking at it," he said. "We've never been a proponent to pay more taxes than we have to." Read MorePfizer-AZ sparks protectionist sound and fury Political pressure to address the tax maneuver has grown in recent years as dozens of companies have bought foreign rivals and moved their headquarters to countries with lower tax rates, reducing revenue to the Treasury. But inversions were thrust into the spotlight last week, when Pfizer became the largest and best-known company to try to essentially renounce its American citizenship. Mr. Levin said companies that moved overseas were unfairly taking advantage of many of the benefits of doing business in the United States but not paying their fair share of taxes.