By-elections and substitutions are methods used to fill seats that have been vacated by an elected representative.
If an MP vacates their seat it is filled by holding a by-election in that constituency.
If an MEP, MLA or local councillor vacates their seat it is filled by substitution. If the elected representative belongs to a political party, the party nominating officer nominates a person to fill their seat. If the elected representative is an Independent, they provide a list of substitutes to the Chief Electoral Officer after they have been elected.
Results of by-elections and substitutions are published on our Homepage as they occur.