Northern Ireland beat Bosnia 4-3 on penalties after a 1-1 draw in the original and extra time, and will play against Slovakia, which needed a penalty shootout to win 4-2 over Ireland after a goalless draw.
Hungary, Iceland, North Macedonia and Georgia also qualified for the play-off final.
Hungary defeated 3-1 at Bulgaria Thanks to goals from Willie Urban, Salt Kalmar and Nemanja Mikulic, Iceland won 2-1 at home to Romania with a double by Gilfi Sigurdsson.
North Macedonia beat its neighbor Kosovo 2-1, to hold fast to the hope of qualifying for the first major tournament since its independence, while Georgia beat Belarus 1-0 after an early penalty kick by Torniki Okriashvili.
Hungary will play home to Iceland, while Georgia will meet North Macedonia in the playoff final.
The European Championship was scheduled to be held between June 12 and July 12 this year, but it was postponed for a year due to the Corona virus pandemic, while the supplement was supposed to play in late March to qualify the last 4 teams to the upcoming sports wedding.