If the U.S. government shuts down, here's how it would work.

If the government does shut down there are some services that will continue no matter, some even if the government were broke.

• Social Security checks would still go out. 
• Tax payments and refunds for e-filed returns Will still be mailed out. 
• Soldiers would remain on duty in Afghanistan and Iraq, and sailors off the coast of Libya. 
• Mail would be delivered.
• Social Security. Checks would still be sent out to current beneficiaries, either through the mail or electronically. (The Obama administration said final plans were still being prepared, and would not say whether the Social Security Administration would be able to handle claims for new beneficiaries.)
• Medicare would still make payments to beneficiaries "at least for a short period of time," according to the senior administration official.
• FBI and other federal law enforcement would keep working

However, a large part of the government  will shut down or have its services affected:

• Roughly 800,000 federal employees would be furloughed, including many civilian workers in the Defense Department, much of the White House staff, and at least some staff in Congress.
• National parks would close.
• Civilians at the Department of Defense. Those whose work helps protect life or property would keep working. Others would be sent home, apparently without pay. "We expect a significant number of DoD civilian employees would be furloughed," the administration official said
  
• The Federal Aviation Administration refused to say whether it would shut down air traffic, referring questions to the Office of Management and Budget. That office didn't respond to questions.
• The EPA would stop doing environmental impact statements and issuing permits, causing some energy and transportation projects to stop. The administration wouldn't say whether the EPA would continue testing to see if radiation from Japan reaches the U.S.
• The SBA would stop approving applications for loans from small businesses.
• The FHA would stop guaranteeing mortgage loans, which could have a significant impact heading into the spring home buying season, the year's busiest. (Administration officials noted that the FHA now guarantees 30 percent of home mortgages, up from 12 percent at the time of the last government shutdown.)
• The FHA would stop guaranteeing mortgage loans, which could have a significant impact heading into the spring home buying season, the year's busiest. (Administration officials noted that the FHA now guarantees 30 percent of home mortgages, up from 12 percent at the time of the last government shutdown)
• AND NO SURPRISE HERE Each member of the House of Representatives and the Senate would decide for themselves which members of their staffs needs to keep working and which could be furloughed, according to the House Administration Committee. Each member would decide "which positions in the office are associated with constitutional responsibilities, the protection of human life, or the protection of property," the committee said.