Immediately — regardless of whether Congress and Obama reach a deal — every working American’s taxes will go up because neither party is fighting to extend a Social Security payroll tax cut that has been in place for two years.
But failure to reach a broader deal on taxes and spending would increase taxes even further, returning rates to Clinton-era levels. January paychecks would shrink as employers start withholding more for taxes.
Many families would also suffer if Congress fails to extend emergency jobless benefits, meaning that 2.1 million Americans would abruptly stop receiving expected payments.
''There’s going to be a hit to people who don’t have much capacity to absorb a hit,’’ said Christine L. Owens of the National Employment Law Project. ‘‘A lot of families are going to be in a bad place, not being able to pay their rent, or their mortgage, or their bills.’’
In short order, such changes are expected to dampen consumer confidence and spending, with potentially grave consequences for an economy already struggling to recover momentum.
‘'Every day that goes by is this needless self-flagellation,’’ said Stuart G. Hoffman, the chief economist of PNC Financial Services Group, who estimated that the tax increases and loss of unemployment benefits would reduce take-home pay by $9 billion a week.
The fallout would continue to worsen if the inaction and stalemate continue.
Tens of millions of families would probably be ensnared by the alternative minimum tax, increasing their 2012 tax bill and potentially throwing the upcoming tax season into disarray. This month the Internal Revenue Service warned that as many as 100 million filers — out of 150 million — could be affected. Analysts said the IRS might have to delay the start of filing season and the delivery of expected refund checks.
Again, the lowest-income families are expected to be hit the hardest. ‘‘Those early filers, 95 percent of them are expecting a healthy refund early in the year,’’ said Mark Steber, the chief tax officer of Jackson Hewitt.
Come mid-January, some Medicare patients also might struggle to find doctors to treat them. Without congressional action, doctors would face two cuts to reimbursement rates: a 26.5 percent reduction in Medicare payment rates from a 1997 law, and a further 2 percent cut adopted to reduce the deficit last year.
‘'I feel I am being held hostage,’’ said Lee R. Rovik, a 70-year-old Medicare beneficiary in Camdenton, Mo. A sign at his doctor’s office warns that it might have to close if Congress does not fix the Medicare payment formula.
''Politicians don’t give a damn about me or the doctor,’’ Rovik said. ‘‘If the clinic goes out of business, which is entirely possible, where will we go?’’
By late February or early March, lawmakers would face another economic showdown over raising the nation’s borrowing limit again to avoid a cash-management crisis and a government shutdown. Republicans have already said they intend to use congressional authority to increase the so-called debt ceiling to extract cuts from entitlement programs — a threat Obama has said he will resist.
Around the same time in early spring, the government and its workers would begin feeling the full effects of cuts to defense and domestic spending.
Without a compromise, the Pentagon and its civilian contractors would face steep reductions in virtually every program. Military officials said those spending reductions — $500 billion over 10 years — would eventually force the canceling or shrinking of projects and large-scale layoffs of military and civilian personnel.
Hundreds of other federal programs would see cuts, beginning in late January and continuing through the year. These include reductions of about 8 percent in the Special Supplemental Nutrition Program for Women, Infants, and Children; the Low-Income Home Energy Assistance Program; and rental housing assistance.
Economists said the spending cuts and tax increases by themselves would smother the recovery. Analysts fear that the economic disruption and political flailing would spook financial markets, amplifying the pain.
''It would be a triple whammy,’’ said Hoffman of PNC, referring to the tax hikes, spending cuts and confidence effects. ‘‘Actually, as many whammies as you could come up with.’’