In the coming weeks we are going to hear a lot about the "debt ceiling." It would help to know exactly what the "debt ceiling" is and is not. The debt ceiling is the amount set by Congress beyond which the U.S. Department of the Treasury cannot borrow. It is not, as some politicians have ranted, a bar to unlimited check writing by the president.
Under U.S. law, an administration can spend only on what Congress has authorized and only if it has sufficient funds to pay for it. These funds can come either from tax receipts or from borrowing by the Treasury. The debt limit does not control or limit the ability of Congress to run deficits or incur obligations; it only restricts Treasury's authority to borrow to finance the decisions already enacted. In other words, it does not stop Congress, with the president's signature of approval, from running up the bills, but it can stop the president from paying them when they come due.
If the debt ceiling is not raised, think of the possibility that the government may not be able to pay for Social Security and Medicare benefits, military salaries and interest and/or principal of U.S. Treasury securities.