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