The US budget deficit more than tripled to a record $1.4 trillion (£877bn) in the year to 30 September, according to US Congress estimates.
Congressional analysts had previously predicted a deficit of $1.6tn but revised their latest estimate, which comes after the end of the fiscal year.
The huge deficit was put down to increased government spending and a big drop in tax revenues.
The Treasury Department will report the actual deficit later this month.
The Congressional Budget Office (CBO) said the deficit was equal to 9.9% of gross domestic product (GDP).
The previous record deficit was $459bn, set last year.
The CBO said the increased spending was due in large part to the government's Troubled Asset Relief Program, the $787bn economic stimulus and the rescue of mortgage giants Fannie Mae and Freddie Mac.
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