Global leaders on Saturday agreed to move ahead with what would be the most significant overhaul of the international tax system in decades, with finance ministers from the world’s 20 largest economies backing a proposal that would crack down on tax havens and impose new levies on large, profitable multinational companies.

If enacted, the plan could reshape the global economy, altering where corporations choose to operate, who gets to tax them and the incentives that nations offer to lure investment. But major details remain to be worked out ahead of an October deadline to finalise the agreement and resistance is mounting from businesses, which could soon face higher tax bills, as well as from small, but pivotal, low-tax countries such as Ireland, which would see their economic models turned upside down.

After spending the weekend huddled in the halls of an ancient Venetian naval shipyard, the top economic officials from the Group of 20 nations agreed to forge ahead. They formally threw their support behind a proposal for a global minimum tax of at least 15 percent that each country would adopt and new rules that would require large global businesses, including technology giants like Amazon and Facebook, to pay taxes in countries where their goods or services are sold, even if they have no physical presence there.

“After many years of discussions and building on the progress made last year, we have achieved a historic agreement on a more stable and fairer international tax architecture,” the finance ministers said in a joint statement, or communiqué, at the conclusion of the meetings.

The approach marks a reversal of years of economic policies that embraced low taxes as a way for countries to attract investment and fuel growth. Instead, countries are coalescing around the view that they must fund infrastructure, public goods and prepare for future pandemics with more fiscal firepower at their disposal, prompting a global hunt for revenue. “I see this deal as being something that’s good for all of us, because as everyone knows, for decades now, the world community, including the United States, we’ve been participating in this self-defeating international tax competition,” Treasury Secretary Janet L. Yellen said on the sidelines of the G20 summit. “I’m really hopeful that with the growing consensus that we’re on a path to a tax regime that will be fair for all of our citizens.”The agreement followed a joint statement last week that was signed by 130 countries who expressed support for a conceptual framework that has been the subject of negotiations at the Paris-based Organization for Economic Cooperation and Development for the better part of the last decade. The O.E.C.D. estimates that the proposal would raise an additional $150 billion of global tax revenue per year and move taxing rights of over $100 billion in profits to different countries.

The backing of the broad framework by the finance ministers on Saturday represented a critical step forward, but officials acknowledged that the hardest part lies ahead as they try to finalise an agreement by the time the leaders of the Group of 20 nations meet in Rome in October. Among the biggest hurdles is an ongoing reluctance by low-tax jurisdictions like Ireland, Hungary and Estonia, which have refused to sign on to the pact, potentially dooming the type of overhaul that Yellen and others envision.

Hungary and Estonia have raised concerns that joining the agreement might violate European Union law and Ireland, which has a tax rate of 12.5 percent, fears that it will upend its economic model, siphoning the foreign investment that has powered its economy. Absent unanimous approval among the members of the European Union, an accord would stall. Establishing a minimum tax would require an E.U. directive, and directives require backing by all 28 countries in the union. Ireland had previously hinted that they would object to or block a directive and Hungary could prove to be an even bigger hurdle given its fraught relationship with the union, which has pressed Hungary on unrelated rule-of-law and corruption issues.

Prime Minister Viktor Orban of Hungary has stated that taxes are a sovereign issue and recently called a proposed global minimum corporate tax “absurd.” Hungary’s low corporate rate of 9 percent has helped it lure major European manufacturers, especially German carmakers including Mercedes and Audi. Bruno Le Maire, France’s finance minister, said on Saturday that it was important that all of Europe supports the proposal. G20 countries plan to meet with Ireland, Hungary and Estonia next week to try and address their concerns, he said.

“We will discuss the point next week with the three countries that still have some doubts,” he said. “I really think the impetus given by the G20 countries is clearly a decisive one and that this breakthrough should gather all European nations together.” Policymakers also have yet to determine the exact rate that companies will pay, with the United States and France pushing to go above 15 percent, and negotiations are continuing over which firms will be subject to the tax and who will be excluded. The framework currently exempts financial services firms and extractive industries such as oil and gas, a carve-out that tax experts have suggested could open a big loophole as companies try to redefine themselves to meet the requirements for exemptions. Domestic politics could also pose hurdles for the countries that have agreed to join but need to turn that commitment into law, including in the United States, where Republican lawmakers have signalled their disapproval, saying the plan would hurt American firms. Big business interests are also warily eyeing the pact and suggesting they plan to fight anything that puts American companies at a disadvantage.

A report this month from the European Network for Economic and Fiscal Policy Research found that only 78 companies are expected to be affected by the overhaul but nearly two-thirds of them are American. The researchers estimated that the new taxes would raise $87 billion in revenue and that Apple, Microsoft, Alphabet, Intel, and Facebook would pay $28 billion of that total.

At the heart of the proposal is the idea that, if countries all agree to a minimum tax, it will prevent businesses from seeking out low-tax jurisdictions for their headquarters, depriving their home countries of revenue. Yellen has criticised what she calls a “race to the bottom” in global taxation.

Yellen said that she would be working in the coming months to address the concerns of countries with reservations but that the deal could still proceed even if some countries did not join. She pointed to an enforcement mechanism that would raise U.S. taxes on corporations that have headquarters in countries that continue to be tax havens but do business in America. Still, changing domestic tax laws will not be quick or easy, including in the United States, whose success in ushering in a new tax regime is being closely watched as a harbinger of whether a global overhaul can come to pass. Senior officials at the G20 meetings said that approval of the agreement within the United States was crucial to its broader acceptance.

The writer is a journalist with NYT©2021

The New York Times