A tactic to avoid corporate taxes has U.S. companies on the move—merging with foreign firms and then setting up residence overseas.
On Monday, Michigan-based medicine manufacturer Perrigo agreed to buy the Irish drug company Elan for $8.6 billion. In the bargain, the combined company's headquarters will be in Ireland, which has a corporate tax rate of 12.5 percent, versus 35 percent in the U.S.
Just the day before, American advertising giant Omnicom Group announced plans for a $35 billion merger with France's Publicis Groupe, saying that the combined company's tax residence will be in the Netherlands, which has a 25 percent corporate tax rate.
(Read more: 3 mergers Cramer says investors shouldn't miss)
Analysts say such mergers are likely to continue.
"Without tax reform in the U.S., I think you will see more of these types of deals," said Ian Shane, a tax lawyer at Golenbock Eiseman Assor Bell & Peskoe.
"You have to start from the premise that most tax laws are a decade behind how business is done," he said. "More companies are global and looking globally, and taxes are part of the bottom line."
Calls to Omnicom from CNBC to discuss the tax issue in detail with were not immediately returned. A spokesman for Perrigo would not give any information on the record for this story.
However, in a conference call for reporters after Perrigo's announcement, Chief Financial Officer Nigel Cherkin acknowledged that being in Ireland would provide the company with more than $2 billion in tax deductions.
And Omnicom's CEO John Wren confirmed in a conference call after his firm's merger announcement that residence in the Netherlands was for tax purposes.
Michael Schwartz, director of accounting and taxes at the advisory firm WeiserMazars, said, "There is a tax on U.S. firms bringing profits from overseas, but if you're incorporated abroad, [the United States] can't tax it if you've merged with another company."