The US budget deficit for the fiscal year 2015 slide to $439 billion, the smallest it has been since 2008, the Treasury Department reported Thursday.

The deficit for this fiscal year, which ended in September, dropped to 2.5% of gross domestic product, according to a report by Reuters. This is the lowest decline since 2007. It is also less than the average deficit for the past 40 years.

Meanwhile, Bloomberg Business reported that the Congressional Budget Office estimated the deficit to be $426 billion. Last year the deficit was $483 billion. That includes a 2.8 % deficit-to-GDP ratio.

The Fiscal 2015 revenue, however, went up to $3.249 trillion, which is an 8 percent increase. Meanwhile, outlays grew to $3.688 trillion, which is a 5 percent increase. The downward slope of the deficit marks a change from the $1 trillion-plus yearly US deficits from 2009 to 2012 caused by the financial crisis the country is facing.

According to WISN, the 8 percent increase in this year's revenue is bolstered by the positive outlook in the job market as individual income taxes went up to almost 11 percent and payroll taxes increased by 6 percent. Corporate taxes also grew by 7 percent.

Congressional leaders have been going into closed-door meetings with the White House to come up with a two-year budget deal. They must reach an agreement by December 11, which is when the funding for federal agencies expires. The Republicans want to take out the limitations on the defense programs budget, while Democrats want to eliminate the caps, not only on defense, but on domestic programs as well. 

There is also a debt ceiling deadline that the Congress should be mindful of. The US government plans to exhausts its borrowing capacity before November 3, according to the Treasury. This is something unacceptable to Republicans, who wants to draw deep reductions in domestic spending in the long term before increasing the government borrowing capacities. Meanwhile, the Treasury recorded a total of $91 billion budget surplus in September. This is a decrease from last year's $106 billion.