The proposal’s sponsors hope to raise nearly $319 billion in tax revenue over a decade and ensure that companies with at least $1 billion in pretax income pay taxes in profitable years, without reducing their income for tax purposes with a range of credits and deductions. Its backers reason that linking the minimum tax to publicly reported financial results will discourage companies from artificially reducing profits, because companies likely won’t risk disappointing investors by engineering smaller profits or even losses to avoid a tax bill.

“The most profitable companies in the world simply don’t want to pay anything,”

Sen. Ron Wyden

(D., Ore.) said in a statement. “Our corporate minimum tax is a backstop to ensure that the most profitable megacorporations are not paying no taxes at all while reporting record profits to their shareholders.”

The legislation’s sponsors say the measure would affect about 200 companies, mostly the biggest publicly traded corporations. A Wall Street Journal analysis of S&P 500 results found about 236 companies met the pretax income threshold last year, and more than 60 reported effective tax rates below 15% in 2019 or 2020.

Under the minimum tax, companies would continue to benefit from a range of general business tax deductions and credits. The most affected companies would likely be in capital-intensive industries, where financial and tax income often diverge more.

Critics call the proposal a recipe for earnings manipulation and confusion. Companies say it will raise costs and reduce business spending. Accounting experts warn that the measure will thrust financial accounting into new territory and risks giving companies an incentive to distort their financial results to reduce their tax burden.

With Friday’s vote, the legislation heads to the Senate, with about $2 trillion in spending and tax cuts, along with a similar amount in offsetting taxes and budgetary savings. Republicans are expected to oppose the package, leaving Democrats unable to lose a single vote in the evenly divided Senate.

Chicago communications-equipment supplier

Motorola Solutions Inc.,

which meets the income threshold and reported effective tax rates of 18.8% in 2020 and 13% in 2019, sees any minimum tax as adding work and costs, said

Helen Carlier,

the company’s global head of tax. But starting with the company’s taxable income base instead of book income would be easier, she said. Book income is the income companies disclose to shareholders, while taxable income is the amount on which companies are taxed after making any allowable revenue deductions.

“You’re building from ground up if you’re going with the book income base as opposed to a variation of a taxable income model, which is remodeling an existing structure,” she said.

Houston utility

CenterPoint Energy Inc.

said the proposal could force it to cut back on infrastructure investment by reducing the tax benefit of making big equipment and other capital purchases, Chief Financial Officer

Jason Wells

said. That’s because there is a timing difference for book and tax purposes on capital expenses.

Companies’ financial statements are generally designed to inform shareholders and allow comparisons across firms, while tax rules collect revenue and can incentivize good behavior, said

Michelle Hutchens,

assistant accounting professor at the University of Illinois at Urbana-Champaign.

Accountants and investors said U.S. accounting rules leave companies more room to lower income than inflate it—the usual concern of investors—through a variety of estimates ranging from loan-loss and litigation reserves to accounts-receivable allowances and warranty estimates. That means companies could push results down in order to reduce their exposure to the minimum tax, said

Jack Ciesielski,

owner of R.G. Associates Inc., an investment research firm and portfolio manager.

And if they could, at least some probably will, said

David Zion,

head of Zion Research Group, an accounting and tax research firm. Companies likely will emphasize nonstandard financial measures to investors, effectively encouraging the markets to look past their formal results.

Such “pro-forma” results have become more widespread in recent decades, with 91% of S&P 500 companies using at least one measure not defined under U.S. generally accepted accounting principles, or GAAP, this year through Thursday, according to MyLogIQ, a data provider.

“This is just another incentive, I guess, to even use that much more non-GAAP,” Mr. Zion said.

The measure’s supporters counter that company auditors, financial-accounting rule-makers and ultimately the Securities and Exchange Commission—which polices public-company disclosure—would all limit companies’ ability to mislead investors and tax authorities.

Motorola’s Ms. Carlier said she isn’t concerned that large public companies would manipulate financial results to reduce their exposure to the minimum tax. “We have external auditors to make sure something like that doesn’t happen,” she said.

Tying taxes more closely to financial accounting also risks undermining the independence of the Financial Accounting Standards Board, which sets GAAP, critics argue. FASB could face political pressure to focus on raising tax revenue instead of its stated mission of ensuring that companies accurately inform investors, Chairman

Rich Jones

said last week. “It would be an additional pressure, there’s no doubt, on our mission and what we do,” he said.

Others note that the nonprofit body already comes under pressure from lawmakers periodically, including recently over new rules on estimating loan losses, which went into effect for large public companies in early 2020.

“There are strict rules around financial accounting, and the Financial Accounting Standards Board has had a long history of objective independence in the face of constant corporate lobbying,” Sen. Wyden said. “I’m very confident that work will continue.”

Write to Mark Maurer at mark.maurer@wsj.com and Theo Francis at theo.francis@wsj.com