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