INDIVIDUAL TAXPAYERS IN THE FUTURE To stay under the $1.5 trillion limit for new deficits lawmakers set for themselves, they opted to make the cuts for individuals and families temporary, expiring at the end of 2025 — even as the corporate tax cuts will be permanent. Republicans are counting on a future Congress to extend the lower rates, as has happened in the past. But there are no guarantees, and that could mean a big tax increase down the road. What is more, the use of a different, less generous measure of inflation would push taxpayers into higher tax brackets more quickly.

THE ELDERLY A 2010 law requires that any legislation that adds to the federal deficit be paid for by spending cuts, increases in revenue or other offsets. Some cuts would be automatic, and the biggest program to be affected is Medicare, the health insurance program for the elderly and disabled. Dozens of other programs are likely to be cut as well, but Medicare, which would face a 4 percent cut, is by far the biggest. Republicans say that this rule will be waived and the cuts will be averted, but that will take a bipartisan deal.

LOW-INCOME FAMILIES Low-income families who claim the earned-income tax credit will lose out on at least $19 billion over the coming decade under the bill because of the change in the way inflation is calculated. And a new requirement that families claiming the child tax credit provide a Social Security number is projected to mean a big reduction in the families claiming it, since those who are not in the United States legally would be prohibited, even if their children were born in the United States.

OWNERS OF HIGH-END HOMES Under current law, the interest on mortgages for first and second homes is deductible for the first $1 million of the loan. The overhaul would cut that to the first $750,000 and eliminate the owner’s ability in the current law to deduct the interest on a home-equity loan up to $100,000. This could drive down home prices in some high-end markets; good for prospective buyers but bad for prospective sellers.

PEOPLE IN HIGH PROPERTY TAX, HIGH INCOME STATES Homeowners in high-tax states like New York, New Jersey and California could be big losers, particularly if they have high property taxes. Their ability to deduct their local property taxes and state and local income taxes from their federal tax bills is now capped at $10,000. In some cases, that could be offset by the lower tax rates that all taxpayers will owe on their ordinary income.

PUERTO RICO Puerto Rico had sought an exemption from new taxes, citing the frail state of its economy nearly three months after Hurricane Maria. But no such luck. The tax bill treats affiliates of American companies on the island as if Puerto Rico were a foreign country and imposes a 12.5 percent tax on intellectual property. Puerto Rico’s governor, Ricardo A. Rosselló, said the tax would hurt the biomedical and technology affiliates that make up about a third of Puerto Rico’s tax base.

THE INTERNAL REVENUE SERVICE The tax collection agency has been underfunded and understaffed for years. Now, it will have a raft of new tax rules to deal with that will require upgrading its software, printing new manuals and explaining to confused taxpayers how things work. All this is expected to take place while the commission is working under the supervision of an interim commissioner, who is expected to be replaced sometime next year.