Under the Senate plan, “Americans are especially likely to face a tax increase if they have a smaller family, have mostly wage income instead of investment income, or claim some of the many deductions that the bill repeals, like those for state and local taxes and employee business expenses,” said Lily Batchelder, a professor and tax specialist at New York University Law School, who worked on economic policy in the Obama administration. “They are increasing taxes on many in the middle class, while concentrating their tax cuts on the wealthy.”

The Senate bill appears much better for the very wealthy than it is for the somewhat wealthy. About half of families earning between two and three times the median income — or about $160,000 to $240,000 for a family of three — would pay more in 2018 than under existing law. But among the richest families, those earning more than about $500,000 for a family of three, nearly 90 percent would get a tax cut.

The findings come with an important caveat: The Senate bill, as written, appears unable to muster the 60 votes needed to avoid a Democratic filibuster, meaning Republicans will need to amend it to comply with the budget reconciliation rules and allow permit passage by a simple majority. Those changes could likely include putting expiration dates on some of the bill’s major provisions, which could make the final version of the bill look less favorable to the middle class, particularly in later years.

The Times’s figures are based on an analysis of Census Bureau data using a tax model from the Open Source Policy Center, a Washington research organization affiliated with the right-leaning American Enterprise Institute. Because the analysis is based on publicly available data, not actual tax records, it may not capture all the intricacies of Americans’ household finances.

The Senate bill differs sharply from the House version in its approach to cutting taxes on businesses. But when it comes to taxes on individuals and families, the bills are more similar than different. Both would double the standard deduction while eliminating a raft of deductions and credits. Both would make the child tax credit more generous. Both would restructure federal income tax brackets to impose lower marginal tax rates at most income levels, although the Senate approach, unlike the House version, doesn’t eliminate two brackets entirely.

The Senate bill includes features that would make its plan more favorable to the middle class. It preserves some popular tax deductions and credits that the House bill initially would have eliminated, and it makes the child tax credit somewhat more generous and widely available. On the other hand, the Senate bill, unlike the House version, would eliminate the deduction for property taxes, which could lead to higher federal taxes for homeowners in areas with high property tax rates or expensive housing markets.

Aparna Mathur, an economist at the American Enterprise Institute, said senators could improve the bill with further changes, such as expanding the earned-income tax credit and extending the benefits of the child tax credit to more low-income taxpayers. “We clearly need to do more to help the lowest-income families,” she said. “At the same time, we can engage in more base broadening for the highest-income households, perhaps by eliminating and not just capping the mortgage-interest deduction.”