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