“When vacancies happen in the Representation from any State, the Executive Authority thereof shall issue Writs of Election to fill such Vacancies.”

— U.S. Constitution, Article I, section 2, clause 4

House vacancies can be caused by death, resignation, declination, withdrawal, or House action, but the Constitution requires that they be filled by election. The law concerning Members elected to fill vacancies varies according to when the vacancy occurs and applicable state law.

All states, territories, and districts require special elections to fill any vacant House seats during the first session of a Congress. During the second session of a Congress, however, procedures often vary depending on the amount of time between the vacancy and the next general election. Section 8 of Title 2, United States Code, provides that a state governor can cause a special election in extraordinary circumstances; namely, a crisis in which the number of House vacancies exceeds 100.

The charts detail the vacancies that have occurred since the 105th Congress (1997–1999) and subsequent action.