"Total debt of the federal government can increase in two ways. First, debt increases when the government sells debt to the public to finance budget deficits and acquire the financial resources needed to meet its obligations. This increases 'debt held by the public'. Second, debt increases when the federal government issues debt to certain government accounts, such as the Social Security, Medicare, and Transportation trust funds, in exchange for their reported surpluses. This increases 'debt held by government accounts'. The sum of 'debt held by the public' and 'debt held by government accounts' is the total federal debt. Surpluses reduce debt held by the public, while deficits raise it. Total federal debt outstanding was $14,025 billion on December 31, 2010. The U.S. Treasury projects the federal debt will reach its statutory limit in spring 2011, although tax policy, spending changes, and economic trends, will affect that timing. Without a debt limit increase, funding federal operations after the middle of 2011 may be complicated. […] In August 2009, Treasury reportedly said that the debt limit would be reached in mid-October, although it later stated that the limit would not be reached until December 2009. H.R. 4314, passed by the House on December 16, 2009, and by the Senate on December 24, raised the debt limit to $12,394 billion when the President signed the measure (P.L. 111-123) on December 28. On January 28, the Senate passed an amended version of H.J.Res. 45, which the House passed on February 4 and the President signed on February 12 (P.L. 111-139), raising the limit to $14,294 billion. This report, written with the assistance of Joseph McCormack, will be updated as events warrant."
CRS Report for Congress, RL31967