In a recent report by Americans for Tax Fairness, Pfizer has been accused of attempting to dodge $35 billion in U.S taxes. Following a new trend in big business, Pfizer plans to merge with Ireland-based Allergan, a move that many are calling tax inversion.

Companies like Pfizer use tax inversions to escape the high corporate tax rate in the US. By merging with a business overseas, the new company can establish a “tax address” in a country with lower rate. Pfizer plans to keep its headquarters in New York City, but establish a new tax address at Allergan’s headquarters in Dublin – shifting from its current U.S. tax rate of 25% down to 18% in Ireland.

Allergan is no stranger to tax inversions; originally a New Jersey-based company, Allergan merged with Ireland’s Actavis, moving their tax address to Dublin just over a year ago.

The Obama administration has announced plans to reduce tax inversions by drafting laws that curb the benefits of a move overseas. Americans for Tax Fairness and a group of five House Democrats are calling for the government to block Pfizer’s $160 billion acquisition of Allegran. In their report, the group claims the merger would allow Pfizer to slash billions from its U.S. tax bill.

But the reported $35 billion in lost U.S. taxes might not be entirely accurate. Americans for Tax Fairness arrived at this number by combining the Pfizer’s 2014 tax liability of $21.1 billion with it’s $74 billion in overseas earnings. Over the past 10 years, Pfizer’s average foreign tax rate has been 18.7%, which ATF used to estimate $13.8 billion in taxes from its $74 billion in overseas earnings. Added to Pfizer’s deferred liability, the total comes to $35 billion. However, Pfizer could continue to defer its tax liability, and it can hold it’s foreign earning overseas nearly indefinitely. That means, even without the Allergan deal, Pfizer can continue to avoid paying out that $35 billion in taxes.

The Pfizer-Allergan merger might not even meet the technical definition of a tax inversion. Because no jobs will be transferred overseas, the government may not have a case to stop the merger. Though Pfizer admits they will benefit from Ireland’s lower corporate tax rate, Pfizer spokeswoman Joan Campion said the move is primarily intended to create a “global, R&D-focused company.”

But if the market is any indication, the merger might not be a sure bet. “The share prices are telling us that there is a great deal of uncertainty about the merger,” Ira Gorsky, a strategist at Elevation L.L.C., a brokerage firm, told the New York Times. As tax inversions become increasingly unpopular with the current administration, this blockbuster merger might be blocked to dissuade other corporations from making similar moves.