Total government income and receipts amounted to $173.861 billion, but expenditures were more than three times as high running at $572.682 billion and generating a monthly deficit of $398.821 billion, the Treasury Department figures showed.
In May, $184 billion were spent on income security, $92 billion on social security, health expenditures stood at $79 billion, and national defence made up $61 billion.
In total, the federal government budget deficit for the first eight months of the current fiscal year, which started on 1 October 2019, has now reached $1.88 trillion - already higher than any full fiscal year 12-month deficit in US history, according to the Treasury Department data.
That eight-month deficit more than doubled the $738.6 billion deficit for the same period in the fiscal year 2019, the report read.