At the core of Republicans’ sprawling domestic policy package is an important political calculation. It provides its most generous tax breaks early on and reserves some of its most painful benefit cuts until after the 2026 midterm elections.

The result is a bill that, if it becomes law, may generate bigger refunds for some taxpayers when they file their returns next spring, even as a series of significant changes to Medicaid and other aid programs loom as a future threat to the finances of poorer families.

For President Trump, the staggered timelines underscore the political risks in his signature legislation, which passed the Senate on Tuesday and now awaits a final vote in the House. To pay for the tax policies, which confer their greatest benefits on the wealthy, Republican lawmakers have looked to slash programs that are both popular and widely used, discomfiting even some within their own ranks.

The savings from the safety net cuts still are not enough to offset an expensive package of tax breaks that is projected to add more than $3 trillion to the federal debt by 2034.

Some of the proposals, including those that could see millions of people lose Medicaid and food stamps, are unlikely to be viewed favorably by voters. That reality led some Senate Republicans to oppose the domestic policy bill this week, citing the potential adverse impacts on their states and residents.

Matthew D. Dickerson, the director of budget policy for the Economic Policy Innovation Center, a conservative group, said the timeline reflected a lesson that Republicans had learned in Mr. Trump’s first term, when they passed a package of tax cuts in 2017.

The legislation, which reduced taxes for most earners, did not take full effect until Americans filed their taxes in 2019. The delay prompted Steven T. Mnuchin, then the Treasury secretary, to cajole companies into lowering the amount of taxes they withheld from paychecks so Americans would feel the benefits of Mr. Trump’s signature law sooner.

Mr. Dickerson said that, this time, “people will see the benefit when they’re filing their taxes next April.”

Alex Jacquez, who served on the National Economic Council under President Joseph R. Biden Jr., said the setup would also allow Republicans to avoid blame for what he described as a set of “fairly disastrous and incredibly unpopular” spending cuts before the midterm election, when future control of the House and Senate will be on the ballot.

“They want to try to get past elections and try to hide the ball on the damage they’re imposing on health care and food assistance,” added Mr. Jacquez, who is now chief of policy at Groundwork Collaborative, a liberal advocacy group.

Starting next year, some taxes may fall

Mr. Trump’s tax package could result in lower taxes for many Americans beginning this year, tax experts have found, with the greatest benefits reserved for the wealthiest taxpayers.

The bill primarily extends the tax breaks enacted in the president’s first term, keeping lower individual income tax brackets intact. That won’t feel like a tax cut to anyone, since it’s just retaining the status quo.

But Americans stand to see some changes when they file ahead of the April 15 tax deadline in 2026. The bill boosts the standard deduction by $750 for individual filers who do not itemize their taxes, except for seniors, who would gain an additional $6,000.

Republicans also aim to expand the amount that households can deduct in state and local taxes on their federal returns. That so-called SALT cap would rise to $40,000 for this year from the current $10,000 limit. It increases slightly each year through 2029, then snaps back to $10,000 in 2030. The policy tends to favor wealthier homeowners living in higher-cost states.

The tax bill delivers on the president’s promise to allow workers to deduct their taxes on tips and overtime pay starting in 2025 through 2028. Not all workers will benefit, however, especially since some people may not make enough money to take full advantage of the new policy. These workers already make less than the amount they can deduct by default, so they see no benefit from the added deduction based on their tips.

Families can claim a larger child tax credit in the current tax year, though poor families who do not report any income cannot take advantage of the credit.

Republicans also extended a set of generous tax breaks for businesses on a permanent basis, which in some cases apply retroactively.

Over time, cuts take effect

Republicans have also included a number of substantial spending cuts targeting safety net programs. As a result, millions of Americans may find their financial situations worse over time.

The initial cuts arrive next year. That’s when millions of people will see changes to the way they enroll in health insurance. Republicans instituted new rules to qualify for subsidies under the Affordable Care Act, including new paperwork burdens and an end to the auto-renewal process.

Customers will begin shopping for those health plans this fall. Several provisions are likely to cause prices for plans to increase, and lower anticipated enrollment could mean some insurers will pare back options or exit markets altogether.

Republicans have pursued more aggressive changes to Medicaid, which helps low-income and disabled Americans obtain health insurance. The bill would require most adults with children age 14 or older to obtain work in order to qualify for aid, while restricting the ways that many states have financed their Medicaid programs.

The new Medicaid work rules are scheduled to take effect after the midterm elections, but the deadline is considered tight by many current and former state officials, given the enormous demands the policy offloads onto state governments to develop new systems for tracking work hours and exemptions for millions of beneficiaries.

The changes to Medicaid financing are parceled out over time. They target so-called provider taxes, a complex funding arrangement that allows most states to collect federal funding to support their Medicaid programs. The most significant cuts in the bill would apply to only a subset of states, and would phase in starting in 2028. States that lose the money will face difficult choices that could result in them cutting payments to medical providers, reducing whom they cover in their programs, or changes elsewhere in state budgets.

A similar timeline applies to Republicans’ substantial cuts to the Supplemental Nutrition Assistance Program, or SNAP, which provides monthly food payments to roughly 42 million families, according to federal data.

Under the bill, more adults who receive food stamps must begin to work in exchange for aid, potentially beginning this year. And starting in 2028, an initial set of states will be required to fund a portion of the benefits, marking the first time that the federal government isn’t shouldering the full financial responsibilities of SNAP.

The nonpartisan Congressional Budget Office has already warned that some states may not be able to fund their share of the program, resulting in millions of Americans seeing reduced or eliminated benefits once the law takes full effect.

Looming changes to clean energy

Many of the bill’s biggest cuts to clean energy subsidies would kick in almost immediately.

Americans who want to buy a new or used electric car will need to get one by Sept. 30 if they want to qualify for consumer tax breaks that are worth up to $7,500. Homeowners who were planning to install rooftop solar panels or install electric heat pumps only have until the end of this year to act before a tax break potentially worth thousands of dollars expires. Previously, all of those credits would have been available into the 2030s.

Similarly, companies hoping to build large-scale wind and solar farms will need to race to beat the deadline. Previously, they would have qualified for a tax break worth at least 30 percent of project costs as long as they began construction by 2034. Now, any new projects will most likely need to start construction within a year of the law’s enactment — so roughly before July 2026 — to order to be certain that they can qualify for the full credit, which quickly disappears after that.

Other phase-outs also come quickly: A tax credit for installing electric vehicle chargers will now expire at the end of June 2026. A credit for making hydrogen fuels only applies to projects that begin construction before the end of 2027. (Other existing tax breaks for developing technologies like nuclear power, geothermal plants, battery storage or carbon capture will stay around until the early 2030s, albeit with new restrictions.)