Discretionary spending occurs through the appropriations process in Congress, as opposed to mandatory spending. Making up about 1/3 of overall spending, it still has a sizable balance sheet — the latest CBO report put it over $1 trillion annually.
By far the largest chunk of the discretionary budget, Pentagon spending counts for about half of all discretionary spending. In 2016, 16 percent of all spending went to the Pentagon.
The regular appropriations process is complex and politically tricky. The process ideally will begin in the early months of the year with the President’s budget request and end as Congress passes the 12 appropriations bills by October.
Although the nation’s largest spending drivers remain on the mandatory side and likely will for the foreseeable future, there are countless opportunities for reform in the discretionary budget. If new military engagements in the Middle East began to ramp up again, or if Congress decides to end the Budget Control Act caps, it’s likely that discretionary spending will become an even more severe drain on finances moving forward.