must chuff
Regular verb: chuff - chuffed- chuffed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must chuff
you must chuff
he must chuff
we must chuff
you must chuff
they must chuff 	I must be chuffing
you must be chuffing
he must be chuffing
we must be chuffing
you must be chuffing
they must be chuffing	I must have chuffed
you must have chuffed
he must have chuffed
we must have chuffed
you must have chuffed
they must have chuffed	I must have been chuffing
you must have been chuffing
he must have been chuffing
we must have been chuffing
you must have been chuffing
they must have been chuffing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't chuff
you mustn't chuff
he mustn't chuff
we mustn't chuff
you mustn't chuff
they mustn't chuff 	I mustn't be chuffing
you mustn't be chuffing
he mustn't be chuffing
we mustn't be chuffing
you mustn't be chuffing
they mustn't be chuffing	I mustn't have chuffed
you mustn't have chuffed
he mustn't have chuffed
we mustn't have chuffed
you mustn't have chuffed
they mustn't have chuffed	I mustn't have been chuffing
you mustn't have been chuffing
he mustn't have been chuffing
we mustn't have been chuffing
you mustn't have been chuffing
they mustn't have been chuffing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I chuff?
must you chuff?
must he chuff?
must we chuff?
must you chuff?
must they chuff? 	must I be chuffing?
must you be chuffing?
must he be chuffing?
must we be chuffing?
must you be chuffing?
must they be chuffing? 	must I have chuffed?
must you have chuffed?
must he have chuffed?
must we have chuffed?
must you have chuffed?
must they have chuffed? 	must I have been chuffing?
must you have been chuffing?
must he have been chuffing?
must we have been chuffing?
must you have been chuffing?
must they have been chuffing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I chuff?
mustn't you chuff?
mustn't he chuff?
mustn't we chuff?
mustn't you chuff?
mustn't they chuff? 	mustn't I be chuffing?
mustn't you be chuffing?
mustn't he be chuffing?
mustn't we be chuffing?
mustn't you be chuffing?
mustn't they be chuffing? 	mustn't I have chuffed?
mustn't you have chuffed?
mustn't he have chuffed?
mustn't we have chuffed?
mustn't you have chuffed?
mustn't they have chuffed? 	mustn't I have been chuffing?
mustn't you have been chuffing?
mustn't he have been chuffing?
mustn't we have been chuffing?
mustn't you have been chuffing?
mustn't they have been chuffing?