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