Many government services do directly use fees to pay for operating the service. Those services can operate with no government appropriation, and the funds never leave the specific agencies' own accounts.

Examples:

* USCIS (source: https://www.aila.org/library/practice-alert-what-happens-if-...)

* 1,823/7,001 Fish and Wildlife service staff (https://www.doi.gov/sites/default/files/documents/2025-09/do...)

* 38,252/74,210 of the FDA (https://www.hhs.gov/about/budget/fy-2026-hhs-contingency-sta...)

* USPS (although as a government owned corporation the separation of funding is more obvious)

* Customs (the actual folks that process tariffs are paid for by the tariffs, unlike border patrol)