WASHINGTON

ON Jan. 1 of next year, the federal tax bill for a typical middle-class household — making in the neighborhood of $50,000 — is scheduled to rise by about $1,750. This increase, which would come from the expiration of both the Bush tax cuts and the Obama stimulus, would follow a decade of little to no income growth for many people. As a result, inflation-adjusted, after-tax income for the median household could fall next year to its 1998 level, in spite of the continuing economic recovery.

The middle-class tax increase is just the beginning of budget changes set to take effect at the start of 2013. Poor families would see their taxes rise somewhat, too. Total federal taxes for top-earning families would rise by tens or even hundreds of thousands of dollars a year. Spending cuts would also take effect, squeezing domestic programs — education, transportation, scientific research — and the military.

All in all, the end of 2012 will be unlike any other time in memory for the federal government.

The tax increases and spending cuts are the result of Washington’s having previously kicked the can down the road, to use a phrase that is popular here. Rather than pass a plan to cut the deficit, policy makers have put off tough decisions. With the Bush tax cuts, lawmakers deliberately made them temporary, to avoid running afoul of budget rules intended to hold down the deficit.

Not surprisingly, leaders of both parties now say they are opposed to letting the changes happen on Jan. 1. Economists are also frightened of what such a sharp shift in government policy might do to a still fragile economy. Ben S. Bernanke, the Federal Reserve chairman, has referred to the various expirations as “a massive fiscal cliff.” Congressional aides, quoted in The Washington Post, call it “taxmageddon.”