Matches were scheduled to be played at the stadium of the team named first on the date specified for each round, which was always a Saturday. If scores were level after 90 minutes had been played, a replay would take place at the stadium of the second-named team later the same week. If the replayed match was drawn further replays would be held at neutral venues until a winner was determined. If scores were level after 90 minutes had been played in a replay, a 30-minute period of extra time would be played.
Calendar
The format of the FA Cup for the season had two preliminary rounds, six qualifying rounds, four proper rounds, and the semi-finals and final.
Round
Date
Extra preliminary round
Saturday 11 September 1920
Preliminary round
Saturday 25 September 1920
First round qualifying
Saturday 9 October 1920
Second round qualifying
Saturday 24 October 1920
Third round qualifying
Saturday 6 November 1920
Fourth Round qualifying
Saturday 20 November 1920
Fifth round qualifying
Saturday 4 December 1920
Sixth round qualifying
Saturday 18 December 1920
First round proper
Saturday 8 January 1921
Second round proper
Saturday 29 January 1921
Third round proper
Saturday 19 February 1921
Fourth round proper
Saturday 5 March 1921
Semi-finals
Saturday 19 March 1921
Final
Saturday 23 April 1921
First round proper
52 of the 66 clubs from the First, Second and Third divisions joined the 12 clubs who came through the qualifying rounds.
Of those sides not receiving a bye to the first round proper, Second Division side Leeds United was entered at the extra preliminary round stage, as the club's admission to the Second Division was agreed by election, rather than obtained through promotion. However, after easy victories against local amateur outfits in their first two matches, the club had to forfeit their first qualifying round tie against Harrogate as it clashed with a League fixture against The Wednesday at Hillsborough. Three sides from the Third Division (Merthyr Town, Newport County and Gillingham) were entered at the fourth qualifying round. Six Third Division and four Second Division sides were entered at the sixth qualifying round stage. These were:
Of these, all of the Third Division sides and Clapton Orient proceeded to the first round proper, in addition to five non-league sides. 32 matches were scheduled to be played on Saturday, 8 January 1921. Six matches were drawn and went to replays in the following midweek fixture, of which one went to another replay.
The 16 second round matches were played on Saturday, 29 January 1921. Five matches were drawn, with replays taking place in the following midweek fixture.
The eight third round matches were scheduled for Saturday, 19 February 1921. One match was drawn and went to a replay in the following midweek fixture. This was also drawn, and so a second replay was played the following week.
The four fourth round matches were scheduled for Saturday, 5 March 1921. There was one replay, between Hull City and Preston North End, played in the following midweek fixture.
The semi-final matches were played on Saturday, 19 March 1921. The Wolverhampton Wanderers–Cardiff City match was drawn and went to a replay four days later. Wolves won this, and went on to meet Tottenham Hotspur in the final.