Although the gap is the highest ever in dollar terms, it is slightly below the forecast for a $445 billion deficit published in late July by the White House.
The new CBO report also said the deficit is projected to decline to $348 billion or 2.8% of GDP, in 2005, but that the budget would remain in the red until 2014.
The deficit has been a key election-year issue, and the latest figures generated further political debate over the administration's economic management.
"Only George Bush could celebrate over a record budget deficit of $422 billion, a loss of 1.6 million jobs and Medicare premiums that are up by a record 17%," Democratic presidential hopeful John Kerry said in a statement.
On the Republican side, House Budget Committee chairman Jim Nussle said the "report underscores that our policies are working to create a stronger economy, more jobs and a lower deficit".
The deficit projected by the non-partisan CBO would be 3.6% of the US gross domestic product (GDP), smaller than the deficits of the mid-1980s and early 1990s relative to the size of the economy.
The deficit projections are also somewhat lower than those made earlier this year by the CBO and the Bush administration, which at one point forecast a gap of $521 billion.
The report said improving economic conditions have boosted government revenues since the March forecast, allowing the CBO to cut its projected deficit for 2004 by $56 billion.
But it also increased its projection for the next 10 years' deficit by $281 billion, based on inflationary projections, higher defence outlays and other technical revisions.
The cumulative deficit for 2005 to 2014 is projected at $2.3 trillion, or 1.5% of total GDP.