US gross national debt surpassed $40tn for the first time on Wednesday, according to the treasury department, marking a milestone reached after the government's deficit doubled over the past decade. The figure underscores years of rising spending under both the Trump and Biden administrations, and comes as Congress remains deadlocked over a spending bill needed to avert a government shutdown at the end of September, while the treasury also faces growing difficulty attracting investors to buy US debt.

The treasury's latest balance stood at $40.047tn as of Tuesday afternoon. During his first term, Donald Trump approved $8.4tn in debt, much of it tied to Covid-19 relief, while Joe Biden approved $4.3tn; so far in fiscal year 2026, $1.8tn has been added, partly driven by $100bn in tariff refunds. Maya MacGuineas of the Committee for a Responsible Federal Budget noted it took nearly 200 years to reach $1tn in debt in 1981, warning that rising borrowing fuels inflation and crowds out other budget priorities. Separately, the treasury announced it would double its buyback of government debt after bond markets reacted to ongoing inflation and US-Iran tensions.