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 couldn't joke you couldn't joke he couldn't joke we couldn't joke you couldn't joke they couldn't joke
V-ing form
I couldn't be joking you couldn't be joking he couldn't be joking we couldn't be joking you couldn't be joking they couldn't be joking
Perfect
I couldn't have joked you couldn't have joked he couldn't have joked we couldn't have joked you couldn't have joked they couldn't have joked
V-ing perfect
I couldn't have been joking you couldn't have been joking he couldn't have been joking we couldn't have been joking you couldn't have been joking they couldn't 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
couldn't I joke? couldn't you joke? couldn't he joke? couldn't we joke? couldn't you joke? couldn't they joke?
V-ing form
couldn't I be joking? couldn't you be joking? couldn't he be joking? couldn't we be joking? couldn't you be joking? couldn't they be joking?
Perfect
couldn't I have joked? couldn't you have joked? couldn't he have joked? couldn't we have joked? couldn't you have joked? couldn't they have joked?
V-ing perfect
couldn't I have been joking? couldn't you have been joking? couldn't he have been joking? couldn't we have been joking? couldn't you have been joking? couldn't they have been joking?