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