In a campaign otherwise light on policy specifics, Vice President Kamala Harris this week quietly rolled out her most detailed, far-ranging proposal yet: nearly $5 trillion in tax increases over a decade.

That’s how much more revenue the federal government would raise if it adopted a number of tax increases that President Biden proposed in the spring. Ms. Harris’s campaign said this week that she supported those tax hikes, which were thoroughly laid out in the most recent federal budget plan prepared by the Biden administration.

No one making less than $400,000 a year would see their taxes go up under the plan. Instead, Ms. Harris is seeking to significantly raise taxes on the wealthiest Americans and large corporations. Congress has previously rejected many of these tax ideas, even when Democrats controlled both chambers.

While tax policy is right now a subplot in a turbulent presidential campaign, it will be a primary policy issue in Washington next year. The next president will have to work with Congress to address the tax cuts Donald J. Trump signed into law in 2017. Many of those tax cuts expire after 2025, meaning millions of Americans will see their taxes go up if lawmakers don’t reach a deal next year.

Here’s an overview of what we now know — and still don’t know — about the Democratic nominee’s views on taxes.

Higher taxes on corporations

The most recent White House budget includes several proposals that would raise taxes on large corporations. Chief among them is raising the corporate tax rate to 28 percent from 21 percent, a step that the Treasury Department estimated could bring in $1.3 trillion in revenue over the next 10 years.

Because the vice president supports the Biden budget’s tax hikes, Ms. Harris has also endorsed raising a tax on stock buybacks to 4 percent from 1 percent. Democrats first approved the stock buyback tax in 2022 as part of the Inflation Reduction Act. The legislation also requires big companies to pay taxes worth at least 15 percent of the income they report to investors. The goal of the new minimum tax is to curb companies’ ability to use deductions and tax credits to shrink their tax liability to as low as zero. Mr. Biden’s budget — and now Ms. Harris’s presidential campaign — calls for increasing that minimum tax to 21 percent from 15 percent.

In his budget, Mr. Biden also put out an overhaul of how multinational companies’ foreign earnings are taxed in the United States. The goal is to bring the United States into compliance with an international agreement that aims to stop companies moving into low-tax jurisdictions to avoid paying taxes. Mr. Biden’s budget calls for increasing and reorganizing a global minimum tax. Under the plan, the tax would be assessed on income in each individual country where the company operates, rather than on its global profits overall. The rate would double to 21 percent from 10.5 percent.

The budget Ms. Harris has now adopted also disallows companies from deducting the compensation of all employees making more than $1 million.

High-earning Americans would pay more

The White House tax plan would raise taxes on high-income Americans through two avenues: First, by increasing the rate they pay on existing income taxes, and second, by more broadly reshaping the taxation of investment gains for the wealthiest taxpayers.

Ms. Harris would set the top marginal income rate at 39.6 percent, up from 37 percent. On top of that, she would also increase the rate on two parallel Medicare surtaxes to 5 percent from 3.8 percent for Americans making more than $400,000 and expand the income subject to one of them. Together, the Medicare and income proposals would create a top marginal rate as high as 44.6 percent.

Wealthy Americans would see more fundamental changes in how gains on investments in stocks, bonds, real estate and other assets are taxed. For Americans making more than $1 million a year, investment earnings would be taxed at the same rate as regular income, instead of at the lower rates for capital gains.

The White House tax plan targets what some Democrats see as a gaping loophole in the tax code: the so-called step-up in basis. Under the current law, Americans owe capital-gains taxes when an asset is sold, but not if they pass those assets on to someone else at the time of their death. That means someone who inherits assets from a deceased parent, for example, does not have to pay taxes on how much those assets appreciated since they were purchased. Instead, the person who inherits the assets has to pay taxes on the gains only from the time they were inherited — and only once they are sold.

Ms. Harris has endorsed a plan to tax the gains on those assets at the original owner’s death, though several exemptions would apply, including when a surviving spouse inherits the assets.

The tax plan would also try to tax the wealthiest Americans’ investment gains before they sell the assets or die. People with more than $100 million in wealth would have to pay at least 25 percent on a combination of their income and their unrealized capital gains — the value of the appreciation in the stocks, bonds, real estate and other assets that they own but haven’t sold. The so-called billionaires-minimum tax could create hefty tax bills for people like Elon Musk who derive much of their wealth from stock they own.

Questions still loom

Ms. Harris’s commitment to the White House budget clarifies much about how she hopes to raise revenue if she wins the election in November. But even the thick White House budget leaves several key tax questions unaddressed, including how exactly Democrats should approach the expiration of key provisions in the Tax Cuts and Jobs Act next year.

The expiring measures included a broader standard deduction, lower marginal income rates for many Americans, and a generous deduction for owners of many closely-held businesses. The White House tax plan states that Americans making less than $400,000 should not see tax increases in a deal. That means that Ms. Harris wants to extend much of the Tax Cuts and Jobs Act, her Republican rival’s signature legislative accomplishment.

Extending the tax cuts for Americans making less than $400,000 could take up much of the roughly $4 trillion cost for continuing all of the lapsing provisions.

Ms. Harris’s campaign has said she would seek to reduce the deficit. But other proposed tax cuts are piling up. On the campaign trail, Ms. Harris has rolled out spending plans and several tax cuts, including a more generous child tax credit, that the Committee for a Responsible Federal Budget estimates could cost roughly $2 trillion over a decade.

This week, Senator Chuck Schumer, a New York Democrat and the majority leader, called for the restoration of a huge tax break: the state and local tax deduction. That deduction is currently capped at $10,000, but the limit expires after next year. Fully restoring the ability of Americans to deduct their state and local taxes from their federal bills could cost roughly $1 trillion over a decade.

So the $5 trillion in tax increases embraced by Ms. Harris this week may not ultimately be enough to cover the cost of her and other Democrats’ ambitions next year.