Interest is now the government's second-largest expense. It passed the Pentagon without a vote.

The finding, in one paragraph: every spending fight in Washington is about the discretionary budget, and the line item that has quietly outgrown almost all of it is the one no committee marks up.▸ Net interest on the federal debt — $722.7 billion in the first eight months of this fiscal year, by the Treasury's own monthly statement — now exceeds the entire national defense function and the entire Medicare function over the same period. It grows for a reason that has nothing to do with this year's deficit: the government's old debt, issued in the 1-to-2 percent world of 2020–2021, matures on schedule and is refinanced at today's rates. The average rate Treasury pays has climbed from 1.61 percent to 3.41 percent in five years and is still below what new debt costs, which means the ratchet has not finished turning even if deficits and yields never move again.

Four sources, each read or pulled directly.▸ The ledger is the Monthly Treasury Statement, Table 9 (May 2026 edition — outlays by function, fiscal year to date), retrieved from Treasury's Fiscal Data API. The rate history is Treasury's Average Interest Rates on U.S. Treasury Securities dataset, same API. The audited totals are GAO's audit of the FY2025 U.S. government consolidated financial statements — roughly $987 billion of interest on debt held by the public in fiscal 2025, on about $30 trillion of public debt plus $7.4 trillion of intragovernmental holdings. The run-rate context is CBO's Monthly Budget Review for June 2026 (released July 9): a $1.4 trillion deficit through nine months, $126 billion in June alone, $1.8 trillion over the trailing twelve months.

Eight-month net interest of $722.7 billion annualizes to roughly $1.08 trillion — a pace consistent with the audited FY2025 figure and CBO's full-year projections.▸ The year-over-year increase, $58.3 billion, is larger than the entire FYTD budget of the Department of Justice function ($68.4 billion) is in total. And "net interest" is the smaller of the government's two official interest numbers: it nets out interest the Treasury pays to its own trust funds. The gross interest expense — the number on the audited books — runs about a quarter-trillion dollars higher, because Social Security's and the military retirement funds' holdings earn interest that is a cost to Treasury even though it stays inside the government.

This is the mechanism the appropriations process never touches.▸ In June 2021 the government's blended borrowing cost was 1.609 percent; five Junes later it is 3.409 percent — not because anyone raised it, but because roughly a third of the marketable debt matures within a year or two and rolls over at market yields. The average remains below the yield on newly issued debt, which is why the line kept climbing in 2025 and 2026 even as the Federal Reserve's policy rate came off its peak. The stock is what does the damage: at $30 trillion of public debt, each tenth of a percentage point on the average is roughly $30 billion a year, indefinitely.

Read the deficit's own components against the headlines about it.▸ Through April, the fiscal-2026 deficit ran $94 billion below the prior year, a statistic that traveled widely; by June's close the nine-month deficit was $35 billion above it. The reversal is in the receipt lines of the same Treasury table. Customs duties collected $188.6 billion in eight months — 132 percent above the prior year — and then went negative in June, as refunds began flowing from the February Supreme Court ruling on the tariffs; the revenue that flattered the spring comparisons is now partially repayable. Corporate income tax receipts are down 30 percent, $209.8 billion against $298.2 billion. Meanwhile the interest line rose on schedule, indifferent to all of it. That is the asymmetry the documents record: the deficit's improvements were contingent and partially reversible; its largest growth item is contractual.

The June Monthly Treasury Statement — the ninth-month official ledger — publishes this week, and the fiscal year closes September 30 with CBO projecting a $1.9 trillion deficit.▸ The refinancing calendar does the rest: Treasury's quarterly refunding announcements set how much of the rollover lands in bills versus long bonds, the one lever that changes the ratchet's speed. The audited FY2026 interest figure arrives with the consolidated financial statements next spring — the same statements GAO cannot render an opinion on, for reasons BlackLeaf has covered.

All figures are from Treasury's Fiscal Data API, GAO's audit of the FY2025 consolidated financial statements, and CBO's June 2026 Monthly Budget Review, as cited in-line. "Net interest" is the MTS budget function (net of intragovernmental receipts); the audited gross interest expense is larger. FYTD figures cover October 2025 through May 2026; June data publish in the next MTS.