I could head you could head he could head we could head you could head they could head
V-ing form
I could be heading you could be heading he could be heading we could be heading you could be heading they could be heading
Perfect
I could have headed you could have headed he could have headed we could have headed you could have headed they could have headed
V-ing perfect
I could have been heading you could have been heading he could have been heading we could have been heading you could have been heading they could have been heading
Negation
Simple form
I could not head you could not head he could not head we could not head you could not head they could not head
V-ing form
I could not be heading you could not be heading he could not be heading we could not be heading you could not be heading they could not be heading
Perfect
I could not have headed you could not have headed he could not have headed we could not have headed you could not have headed they could not have headed
V-ing perfect
I could not have been heading you could not have been heading he could not have been heading we could not have been heading you could not have been heading they could not have been heading
Interrogative form
Simple form
could I head? could you head? could he head? could we head? could you head? could they head?
V-ing form
could I be heading? could you be heading? could he be heading? could we be heading? could you be heading? could they be heading?
Perfect
could I have headed? could you have headed? could he have headed? could we have headed? could you have headed? could they have headed?
V-ing perfect
could I have been heading? could you have been heading? could he have been heading? could we have been heading? could you have been heading? could they have been heading?
Interro-negative form
Simple form
could I not head? could you not head? could he not head? could we not head? could you not head? could they not head?
V-ing form
could I not be heading? could you not be heading? could he not be heading? could we not be heading? could you not be heading? could they not be heading?
Perfect
could I not have headed? could you not have headed? could he not have headed? could we not have headed? could you not have headed? could they not have headed?
V-ing perfect
could I not have been heading? could you not have been heading? could he not have been heading? could we not have been heading? could you not have been heading? could they not have been heading?