I could come you could come he could come we could come you could come they could come
V-ing form
I could be coming you could be coming he could be coming we could be coming you could be coming they could be coming
Perfect
I could have come you could have come he could have come we could have come you could have come they could have come
V-ing perfect
I could have been coming you could have been coming he could have been coming we could have been coming you could have been coming they could have been coming
Negation
Simple form
I couldn't come you couldn't come he couldn't come we couldn't come you couldn't come they couldn't come
V-ing form
I couldn't be coming you couldn't be coming he couldn't be coming we couldn't be coming you couldn't be coming they couldn't be coming
Perfect
I couldn't have come you couldn't have come he couldn't have come we couldn't have come you couldn't have come they couldn't have come
V-ing perfect
I couldn't have been coming you couldn't have been coming he couldn't have been coming we couldn't have been coming you couldn't have been coming they couldn't have been coming
Interrogative form
Simple form
could I come? could you come? could he come? could we come? could you come? could they come?
V-ing form
could I be coming? could you be coming? could he be coming? could we be coming? could you be coming? could they be coming?
Perfect
could I have come? could you have come? could he have come? could we have come? could you have come? could they have come?
V-ing perfect
could I have been coming? could you have been coming? could he have been coming? could we have been coming? could you have been coming? could they have been coming?
Interro-negative form
Simple form
couldn't I come? couldn't you come? couldn't he come? couldn't we come? couldn't you come? couldn't they come?
V-ing form
couldn't I be coming? couldn't you be coming? couldn't he be coming? couldn't we be coming? couldn't you be coming? couldn't they be coming?
Perfect
couldn't I have come? couldn't you have come? couldn't he have come? couldn't we have come? couldn't you have come? couldn't they have come?
V-ing perfect
couldn't I have been coming? couldn't you have been coming? couldn't he have been coming? couldn't we have been coming? couldn't you have been coming? couldn't they have been coming?