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 couldn't head you couldn't head he couldn't head we couldn't head you couldn't head they couldn't head
V-ing form
I couldn't be heading you couldn't be heading he couldn't be heading we couldn't be heading you couldn't be heading they couldn't be heading
Perfect
I couldn't have headed you couldn't have headed he couldn't have headed we couldn't have headed you couldn't have headed they couldn't have headed
V-ing perfect
I couldn't have been heading you couldn't have been heading he couldn't have been heading we couldn't have been heading you couldn't have been heading they couldn't 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
couldn't I head? couldn't you head? couldn't he head? couldn't we head? couldn't you head? couldn't they head?
V-ing form
couldn't I be heading? couldn't you be heading? couldn't he be heading? couldn't we be heading? couldn't you be heading? couldn't they be heading?
Perfect
couldn't I have headed? couldn't you have headed? couldn't he have headed? couldn't we have headed? couldn't you have headed? couldn't they have headed?
V-ing perfect
couldn't I have been heading? couldn't you have been heading? couldn't he have been heading? couldn't we have been heading? couldn't you have been heading? couldn't they have been heading?