What Is the US Debt Limit and Why Does It Matter?

With total US government debt recently surpassing $40 trillion, the nation’s debt limit is back in the news. Congress most recently increased the debt limit in July 2025, from $36.1 trillion to $41.1 trillion, under the One Big Beautiful Bill Act.

While the US government has faced several close calls on its debt payments over its 250-year history, a major default would be unprecedented. Congress has raised or suspended the debt limit dozens of times over the past century. But recent fights over when and how to do so have brought the US to the brink of default.

Default should not be an option for policymakers. The economic consequences of the US failing to meet its debt obligations should be too great for lawmakers to even approach the brink. However, the limit remains one of the only brakes on runaway debt and deficits. Any reforms to the process should maintain or increase opportunities for Congress to debate and improve the fiscal health of the nation.

What Is the Debt Limit?

The debt limit is a legal ceiling on how much the US Treasury Department can issue in outstanding obligations. put it another way, it sets a maximum amount for government borrowing. Importantly, the debt limit does not commit Congress to new spending; it allows the US government to pay the bills it has already incurred. Table 1 below describes in brief some fiscal terms that will be used throughout this piece.

Table 1. Key Fiscal Terms, Defined

Source: Grant A. Driessen, “The Debt Limit,” Congressional Research Service, Updated Sep. 21, 2026, https://www.congress.gov/crs_external_products/IF/PDF/IF10292/IF10292.22.pdf; Treasury Department, “Daily Treasury Statement,” Accessed Oct. 26, 2026, https://fiscaldata.treasury.gov/datasets/daily-treasury-statement/operating-cash-balance; Congressional Budget Office, “Monthly Budget Review: September 2026,” Oct. 8, 2026, https://www.cbo.gov/publication/61985.

While simple in concept, the mechanics of the debt limit are complicated. The current limit is $41.1 trillion, but the government won’t simply default when it appears as if total public debt outstanding is about to hit that mark.

Instead, the Treasury Department can use several so-called “extraordinary measures” that enable it to delay the day the government actually hits the debt limit. The measures include pausing investments and reinvestments in federal employee retirement funds the government manages and suspending the issuance of new debt. The most common extraordinary measures are described in Table 2 below.




Table 2. Description of Treasury’s Debt Limit Extraordinary Measures and How Much Headroom They Provide Under the Debt Limit

Note: References to “one time” measures for the G Fund and ESF actually require daily action by the Treasury Department. Essentially, Treasury declines to reinvest G Fund and ESF securities on a daily basis. These measures are listed as “one time” because the balance—which fluctuates—is the amount of savings available as an extraordinary measure. For example, two days of Treasury suspending G Fund reinvestment does not create $596 billion of headroom ($298 billion x 2). It creates $298 billion of headroom each day Treasury exercises the option.
Source: Treasury Department, “Description of the Extraordinary Measures,” Jan. 17, 2025, https://home.treasury.gov/system/files/136/DescriptionofExtraordinaryMeasures20250117.pdf.

Exactly when the US government will next reach the debt limit remains highly uncertain, but one often cited estimate from the Bipartisan Policy Center (BPC) puts that date—the so-called “X Date”—at sometime in 2027. BPC’s estimate incorporates Treasury’s use of extraordinary measures.

History of the Debt Limit

The debt limit in its modern form has been around since 1939, though policymakers have acted to limit the government’s borrowing through various ways and means since before the nation was a nation. The 1939 law consolidated a number of different limits into one, combined public debt limit of $45 billion (approximately $1.1 trillion in 2026 dollars). The limit ballooned to $300 billion in 1945 to accommodate World War II debt ($5.7 trillion in 2026 dollars). Since then, Congress has increased, suspended, or modified the limit 118 times.

The debt limit has taken on new importance in the 21^st century, as US government debt and deficits ascend to levels never before seen in peacetime. At the turn of the century, the debt limit was just shy of $6.0 trillion ($12.0 trillion in 2026 dollars).

During that time, Congress has had several protracted debates over the debt limit—in 2011, 2013, 2015, 2019, and 2023, for example—that have raised questions over whether the US would default. While the US did not default during those episodes, two of them contributed to credit rating agencies downgrading US government debt from its previous gold-standard AAA rating—S&P in 2011 and Fitch in 2023.

Why Does the Debt Limit Matter?

The debt limit is a flawed instrument for improving the US fiscal trajectory. It is also one of the only ones left. In the 1990s, bipartisan budget agreements and a roaring economy lent the US budget surpluses and declining debt. Since then, decades of deficit-financed spending increases and taxA tax is a mandatory payment or charge collected by local, state, and national governments from individuals or businesses to cover the costs of general government services, goods, and activities. cuts have produced an increasingly unsustainable budget situation.

The nonpartisan Congressional Budget Office (CBO) projects that the gap between government spending and revenue will continue to grow in the years ahead. CBO estimates that annual deficits regularly surpass $2 trillion per year, and that debt held by the public will increase from $32 trillion in 2026 to $168 trillion in 2056 (and from 100 percent of GDP to 175 percent over the same period).

While CBO’s forecast does not include any legislative efforts to reduce debt and deficits, it also does not include any major, negative shocks to the nation or its economy (e.g., wars, recessions, pandemics, or other crises). In some sense, then, this outlook actually underscores the potential budgetary and economic peril if Congress fails to act.

So, what are the alternatives to the debt limit?

Some policymakers have proposed repealing it. Doing so without broader fiscal reforms would be a mistake.

Other policymakers have hinted at potentially letting the US default. Default would be an even greater mistake than repealing the debt limit. A default could lead to a permanent increase in US borrowing costs. Higher borrowing costs would further widen the gap between spending and revenue, and increase the likelihood that economically damaging tax increases are needed to close the gap. A default could also delay Social Security and military payments and rattle global markets that treat Treasury bonds as a risk-free asset.

A middle path might be bipartisan debt limit reform that takes the worst of the brinksmanship off the table while establishing more regular intervals for Congress to debate and enact fiscal reforms. Reps. Bill Huizenga (R-MI) and Scott Peters (D-CA) have proposed one such reform, the Responsible Budgeting Act.

Debt Limit Reform Principles

Policymakers could apply Tax Foundation’s four principles of sound tax policy to the debt limit debate:

• Simplicity: Debt limit reform should be easy for lawmakers and the public to understand. It should unlock straightforward windows for debt and deficit reduction that don’t rely on byzantine congressional procedure.
• Neutrality: Debt limit reform should not put the thumb on the scale for tax increases over spending cuts (or vice versa). Instead, it should leave those decisions to policymakers—procedure and policy should be separate.
• Transparency: Reform should lead to fiscal discussions that are open to policymakers and US citizens.
• Stability: Debt limit reform should offer predictable opportunities to reduce deficits that increase taxpayer and investor confidence in the US budgetary outlook and stabilize debt and deficit levels.

Big Picture

A $40 trillion total government debt—and rising—guarantees that Congress will soon be discussing the debt limit again. At its worst, the debt limit symbolizes a dysfunctional Washington that has yet to rein in an unsustainable budget trajectory. At its best, it represents one of the last, best brakes on runaway debt and spending. Debt limit reform should be simple, transparent, and neutral on policy direction, and it should create more opportunities to stabilize the fiscal outlook.

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