Spending outpaced revenue between the beginning of the fiscal year, on Oct. 1, and July by $682 billion, $116 billion more than over the same period in the last fiscal year.
The rising deficit is largely the result of the tax cuts President Trump signed into law at the end of last year, as well as a bipartisan agreement to boost spending, according to CBO.
Tax revenues from individuals rose, even as revenues from corporate taxes dropped.
The Trump administration has argued that the tax cuts would bring down the deficit, as economic growth led to higher tax revenue. The economy did expand in the second quarter by 4.1 percent.
But economists have argued the growth would have to be much larger to reduce the deficit.
The CBO projects that the deficit will reach $793 billion by the end of the year and approach $1 trillion next year. White House estimates have the deficit surpassing $1 trillion in 2019.
Budget watchers have warned that interest payments - the amount the Treasury has to pay just to service the debt - are slated to become the fastest-growing annual expenditure.
The CBO projects that in 30 years, the government will spend more on servicing debt than on Social Security or defense.