The writer is a professor of economics and finance at Columbia University and previously chaired the US Council of Economic Advisers

From the Biden administration’s inception, US Treasury Secretary Janet Yellen has championed a global minimum tax for corporations. While the US walked back from a request for a 21 per cent rate (which was linked to an objective of raising the current US corporate tax of 21 per cent to between 25 and 28 per cent), it did lock in with G7 finance ministers a rate of at least 15 per cent. Secretary Yellen praised the move: “That global minimum tax would end the race to the bottom in corporate taxation, and ensure fairness for the middle class and working people in the US and around the world.”

It is tough to argue that corporate income shouldn’t pay its “fair share”. But the global minimum tax raises both political and economic questions.

Politics first. Approval in the US is likely to be tough. The minimum tax is estimated by the OECD to raise as much as $50bn-$80bn per year, much of it from successful American firms. Revenue to the US Treasury would be part of this amount, but small relative to the substantial expansion in spending proposed by the Biden administration. Will other governments engage their own political costs to achieve a deal that may be ephemeral if it fails to get US legislative approval? Even if the deal succeeds, might it hand a competitive victory to China? As a non-party to G7 or OECD proposals, could it not use both tax rates and subsidies to draw more investment to China?

But it is on economics that the global minimum tax draws more sensitive questions in two areas. The first is the design of the tax base. The second addresses the foundational question of the problem policymakers are trying to solve and whether the new minimum tax is the best way to do so.

A 15 per cent rate is not particularly useful without an agreement on what the tax base is. Particularly for the US, home to many very profitable technology companies, the concern should arise that countries will use special taxes and subsidies that effectively target certain industries. The US has had a version of a minimum tax of foreign earnings since the Tax Cuts and Jobs Act of 2017 enshrined GILTI (Global Intangible Low-Taxed Income) provision into law. The Biden administration wants to use the new global minimum tax to raise the GILTI rate and expand the tax base by eliminating a GILTI deduction for overseas plant and equipment investments.

For a 15 per cent minimum rate to make sense, countries would need a uniform tax base. Presumably, the goal of the new minimum tax is to limit the benefits to companies of shifting profits to low-tax jurisdictions, not to distort where those firms invest. The combination of a global minimum tax with the broad base advocated by the Biden administration could reduce cross-border investments and reduce the profitability of large multinational firms.

A still deeper economic issue is that of who bears the tax burden. I noted above that projected revenue increases are small compared to G7 government spending levels. It is not corporations who would pay more, but capital owners generally and workers, according to contemporary economic views of who bears the burden of the tax.

There is a better way to achieve what Yellen and her finance minister colleagues are trying to accomplish. To begin with, countries could allow full expensing of investment. That approach would move the tax system away from a corporate income tax toward a cash flow tax, long favoured by economists. In this revision, the minimum tax would not distort new investment decisions. It would also push the tax burden on to economic rents — profits in excess of the normal return to capital — better satisfying the apparent G7 goal of garnering more revenue from the most profitable large companies. And such a system would be simpler to administer, as multinationals would not need to set up different ways to track deductible investment costs over time in different countries.

In the debate leading up to the 2017 US tax law changes, Congress considered a version of this idea in a destination-based cash flow tax. Like a value added tax, this would tax corporate profits based on cash flows in a given country. The reform, which foundered on the political desirability of border adjustments, limits tax biases against investment and boosts tax fairness.

Returning to the numbers: countries with large levels of public spending relative to gross domestic product, as the Biden administration proposes, fund it mainly with value added taxes, not traditional corporate income taxes. A better global tax system is possible, but it starts with a verdict of “not GILTI”.

Letter in response to this article:

A G7 tax deal must not risk poorer states’ competitiveness / From Piotr Arak, Director, Polish Economic Institute Warsaw, Poland