A government shutdown occurs when the legislative branch (Congress) fails to pass key funding bills or a temporary funding measure to finance government operations for the new fiscal year. Without approved appropriations bills, the government is legally required to cease non-essential functions, furlough non- essential employees, and keep only essential services—especially those protecting human life or property—operating. This shutdown halts many federal programs and services until new funding legislation is passed and signed by the president.

In the U.S., government shutdowns arise from political impasses during budget negotiations, often around differing priorities between the parties or the president and Congress. A shutdown can begin at midnight on the fiscal year's start if no agreement is reached, as recently happened in October 2025 when Democrats and Republicans, including President Trump, failed to agree on a stopgap funding measure.

The shutdown process includes furloughing non-essential workers who do not receive pay during the shutdown but often receive back pay once the shutdown ends. Essential agencies such as the FBI and CIA continue operating but may also face operational constraints due to lack of funding.

In summary, a government shutdown is triggered legally by the failure to pass funding appropriations before the fiscal year begins, leading to a suspension of many government activities until the funding impasse is resolved.