A U.S. government shutdown is possible on Tuesday, the first day of fiscal 2014, because Congress has so far failed to find a way to pay for it.
A closure would have far-reaching consequences at federal agencies dealing with everything from sending out Social Security checks to collecting admission fees at national parks.
Here is a roundup of how the impact would be felt:
Federal workers: As many as 1 million U.S. federal employees could face unpaid furloughs or payless paydays, according to the president of the American Federation of Government Employees, which represents 670,000 union members.
National parks: National parks would close, meaning a loss of 750,000 daily visitors and an economic loss to gateway communities of as much as $30 million for each day parks are shut, according to the non-profit National Parks Conservation Association.
(Read more: Last shutdown is a lesson lost on Capital Hill)
Defense Department: All military personnel would continue on normal duty status, but many civilian employees would be temporarily furloughed, Deputy Defense Secretary Ashton Carter said in a memo. He said furlough notices would be issued on Tuesday, Oct. 1, if no agreement to fund the government is reached.
The ratings agency Standard & Poor's said a shutdown of less than two weeks would not materially affect the credit of big defense contractors, though a longer shutdown could weaken smaller defense contractors. Most defense contractors would not be paid, new contracts would not start and orders would be delayed, with service contracts hardest hit, S&P said.
Internal Revenue Service: Most of the federal tax agency's 90,000 employees would be furloughed. Taxpayers who requested an extension beyond the April 15 deadline to file their 2012 taxes must do so by Oct. 15, and they will still be able to file these returns even if the IRS is still shut down then.