I could joke you could joke he could joke we could joke you could joke they could joke
V-ing form
I could be joking you could be joking he could be joking we could be joking you could be joking they could be joking
Perfect
I could have joked you could have joked he could have joked we could have joked you could have joked they could have joked
V-ing perfect
I could have been joking you could have been joking he could have been joking we could have been joking you could have been joking they could have been joking
Negation
Simple form
I could not joke you could not joke he could not joke we could not joke you could not joke they could not joke
V-ing form
I could not be joking you could not be joking he could not be joking we could not be joking you could not be joking they could not be joking
Perfect
I could not have joked you could not have joked he could not have joked we could not have joked you could not have joked they could not have joked
V-ing perfect
I could not have been joking you could not have been joking he could not have been joking we could not have been joking you could not have been joking they could not have been joking
Interrogative form
Simple form
could I joke? could you joke? could he joke? could we joke? could you joke? could they joke?
V-ing form
could I be joking? could you be joking? could he be joking? could we be joking? could you be joking? could they be joking?
Perfect
could I have joked? could you have joked? could he have joked? could we have joked? could you have joked? could they have joked?
V-ing perfect
could I have been joking? could you have been joking? could he have been joking? could we have been joking? could you have been joking? could they have been joking?
Interro-negative form
Simple form
could I not joke? could you not joke? could he not joke? could we not joke? could you not joke? could they not joke?
V-ing form
could I not be joking? could you not be joking? could he not be joking? could we not be joking? could you not be joking? could they not be joking?
Perfect
could I not have joked? could you not have joked? could he not have joked? could we not have joked? could you not have joked? could they not have joked?
V-ing perfect
could I not have been joking? could you not have been joking? could he not have been joking? could we not have been joking? could you not have been joking? could they not have been joking?