A by-election to replace Sinn Fein's Martin McGuinness will be held on March 7, MPs have been told.
Chief whip Sir George Young initiated the election process by moving a writ for the Mid Ulster seat in the Commons.
The Deputy First Minister of Northern Ireland announced last year that he would resign as an MP and formally left his seat on January 2.
Sinn Fein has pledged to end the practice of its representatives holding seats in more than one elected assembly.
Like all Sinn Fein MPs, Mr McGuinness never took his seat in the Commons.