WASHINGTON -- Everyone who pays income tax -- and some who don't -- will feel it.
So will doctors who accept Medicare, people who get unemployment aid, defense contractors, air traffic controllers, national park rangers and companies that do research and development.
The package of tax increases and spending cuts known as the "fiscal cliff" takes effect in January unless Congress passes a budget deal by then. The economy would be hit so hard that it would likely sink into recession in the first half of 2013, economists say.
And no matter who you are, it will be all but impossible to avoid the pain.
Middle-income families would have to pay an average of about $2,000 more next year, the nonpartisan Tax Policy Center has calculated.
Up to 3.4 million jobs would be lost, the Congressional Budget Office estimates.
The unemployment rate would reach 9.1 percent from the current 7.9 percent. Stocks could plunge.
The nonpartisan CBO estimates the total cost of the cliff in 2013 at $671 billion.
Collectively, the tax increases would be the steepest to hit Americans in 60 years when measured as a percentage of the economy.
"There would be a huge shock effect to the U.S. economy," says Mark Vitner, an economist at Wells Fargo.
Most of the damage -- roughly two-thirds -- would come from the tax increases. But the spending cuts would cause pain, too.
The bleak scenario could push the White House and Congress to reach a deal before year's end. On Tuesday, Congress returned for a post-election session that could last through Dec. 31. At a minimum, analysts say some temporary compromise might be reached, allowing a final deal to be cut early next year.
Still, uncertainty about a final deal could cause many companies to further delay hiring and spend less. Already, many companies say anxiety about the fiscal cliff has led them to put off plans to expand or hire.
A breakdown in negotiations also could ignite turmoil in financial markets, Vitner said. It could resemble the 700-point fall in the Dow Jones industrial average in 2008 after the House initially rejected the $700 billion bailout of major banks.
Since President Barack Obama's re-election, nervous investors have sold stocks. The Standard & Poor's 500 index sank 2.3 percent last week, its worst weekly drop since June. The sell-off resulted in part from anxiety over higher tax rates on investment gains once the fiscal cliff kicks in.
Last week, Obama said he was open to compromise with Republican leaders. But the White House said he would veto any bill that would extend tax cuts on income of more than $250,000.
House Speaker John Boehner, R-Ohio, countered that higher tax rates on upper-income Americans would slow job growth. He argued that any deal must cut tax rates, eliminate special-interest loopholes and rein in government benefits.
The government has run annual deficits in excess of $1 trillion in each of the last four fiscal years. A report Tuesday showed the government started the 2013 budget year with a $120 billion deficit in October, suggesting a fifth $1 trillion annual deficit is likely.
That adds pressure on Obama and Congress to reach a budget deal.
Still, most economists want an agreement that would lower the deficit gradually over several years, rather than a sharp cut that could rattle the still-weak economy.