I must joke you must joke he must joke we must joke you must joke they must joke
V-ing form
I must be joking you must be joking he must be joking we must be joking you must be joking they must be joking
Perfect
I must have joked you must have joked he must have joked we must have joked you must have joked they must have joked
V-ing perfect
I must have been joking you must have been joking he must have been joking we must have been joking you must have been joking they must have been joking
Negation
Simple form
I mustn't joke you mustn't joke he mustn't joke we mustn't joke you mustn't joke they mustn't joke
V-ing form
I mustn't be joking you mustn't be joking he mustn't be joking we mustn't be joking you mustn't be joking they mustn't be joking
Perfect
I mustn't have joked you mustn't have joked he mustn't have joked we mustn't have joked you mustn't have joked they mustn't have joked
V-ing perfect
I mustn't have been joking you mustn't have been joking he mustn't have been joking we mustn't have been joking you mustn't have been joking they mustn't have been joking
Interrogative form
Simple form
must I joke? must you joke? must he joke? must we joke? must you joke? must they joke?
V-ing form
must I be joking? must you be joking? must he be joking? must we be joking? must you be joking? must they be joking?
Perfect
must I have joked? must you have joked? must he have joked? must we have joked? must you have joked? must they have joked?
V-ing perfect
must I have been joking? must you have been joking? must he have been joking? must we have been joking? must you have been joking? must they have been joking?
Interro-negative form
Simple form
mustn't I joke? mustn't you joke? mustn't he joke? mustn't we joke? mustn't you joke? mustn't they joke?
V-ing form
mustn't I be joking? mustn't you be joking? mustn't he be joking? mustn't we be joking? mustn't you be joking? mustn't they be joking?
Perfect
mustn't I have joked? mustn't you have joked? mustn't he have joked? mustn't we have joked? mustn't you have joked? mustn't they have joked?
V-ing perfect
mustn't I have been joking? mustn't you have been joking? mustn't he have been joking? mustn't we have been joking? mustn't you have been joking? mustn't they have been joking?