Other parts of the law, however, put restrictions on inherited I.R.A.s, and if you have one or are thinking of bequeathing one, it’s worth paying attention.

The old rules were comparatively simple.

Before this year, those lucky enough to inherit an individual retirement account had to take some money out of it each year. However, they could “stretch” out the withdrawals over their lifetimes — years or even decades, depending on their age when they came into the money. They were able to withdraw small amounts annually, to soften the impact on their income taxes, while keeping the balance invested.

“You could take little crumbs out, and let it grow tax-deferred over decades,” said Ed Slott, a certified public accountant and I.R.A. expert in Rockville Centre, N.Y. Required annual withdrawals were based on life expectancy, so the technique was especially helpful for young children or grandchildren, whose mandatory withdrawals would be quite small.

Now, heirs have just 10 years to drain an account.

Under the new rules, many people who inherit an I.R.A. must now empty it, and pay any required taxes, within 10 years. That means some people could end up having to pay more in income taxes, and will have less time for the money to remain invested and grow. Someone who inherits an I.R.A. from a parent at age 55, for example, might be at her peak earning period, and would prefer to delay adding to her income to avoid higher taxes. Now, though, she must drain the funds within a decade, said David Flores Wilson, a certified financial planner in New York City.

The new rules apply to accounts inherited after Dec. 31, 2019. Heirs of I.R.A. owners who died in 2019 and earlier can still use the stretch approach.