I could mess you could mess she could mess we could mess you could mess they could mess
V-ing form
I could be messing you could be messing she could be messing we could be messing you could be messing they could be messing
Perfect
I could have messed you could have messed she could have messed we could have messed you could have messed they could have messed
V-ing perfect
I could have been messing you could have been messing she could have been messing we could have been messing you could have been messing they could have been messing
Negation
Simple form
I could not mess you could not mess she could not mess we could not mess you could not mess they could not mess
V-ing form
I could not be messing you could not be messing she could not be messing we could not be messing you could not be messing they could not be messing
Perfect
I could not have messed you could not have messed she could not have messed we could not have messed you could not have messed they could not have messed
V-ing perfect
I could not have been messing you could not have been messing she could not have been messing we could not have been messing you could not have been messing they could not have been messing
Interrogative form
Simple form
could I mess? could you mess? could she mess? could we mess? could you mess? could they mess?
V-ing form
could I be messing? could you be messing? could she be messing? could we be messing? could you be messing? could they be messing?
Perfect
could I have messed? could you have messed? could she have messed? could we have messed? could you have messed? could they have messed?
V-ing perfect
could I have been messing? could you have been messing? could she have been messing? could we have been messing? could you have been messing? could they have been messing?
Interro-negative form
Simple form
could I not mess? could you not mess? could she not mess? could we not mess? could you not mess? could they not mess?
V-ing form
could I not be messing? could you not be messing? could she not be messing? could we not be messing? could you not be messing? could they not be messing?
Perfect
could I not have messed? could you not have messed? could she not have messed? could we not have messed? could you not have messed? could they not have messed?
V-ing perfect
could I not have been messing? could you not have been messing? could she not have been messing? could we not have been messing? could you not have been messing? could they not have been messing?