I could do you could do he could do we could do you could do they could do
V-ing form
I could be doing you could be doing he could be doing we could be doing you could be doing they could be doing
Perfect
I could have done you could have done he could have done we could have done you could have done they could have done
V-ing perfect
I could have been doing you could have been doing he could have been doing we could have been doing you could have been doing they could have been doing
Negation
Simple form
I could not do you could not do he could not do we could not do you could not do they could not do
V-ing form
I could not be doing you could not be doing he could not be doing we could not be doing you could not be doing they could not be doing
Perfect
I could not have done you could not have done he could not have done we could not have done you could not have done they could not have done
V-ing perfect
I could not have been doing you could not have been doing he could not have been doing we could not have been doing you could not have been doing they could not have been doing
Interrogative form
Simple form
could I do? could you do? could he do? could we do? could you do? could they do?
V-ing form
could I be doing? could you be doing? could he be doing? could we be doing? could you be doing? could they be doing?
Perfect
could I have done? could you have done? could he have done? could we have done? could you have done? could they have done?
V-ing perfect
could I have been doing? could you have been doing? could he have been doing? could we have been doing? could you have been doing? could they have been doing?
Interro-negative form
Simple form
could I not do? could you not do? could he not do? could we not do? could you not do? could they not do?
V-ing form
could I not be doing? could you not be doing? could he not be doing? could we not be doing? could you not be doing? could they not be doing?
Perfect
could I not have done? could you not have done? could he not have done? could we not have done? could you not have done? could they not have done?
V-ing perfect
could I not have been doing? could you not have been doing? could he not have been doing? could we not have been doing? could you not have been doing? could they not have been doing?