I could forget you could forget he could forget we could forget you could forget they could forget
V-ing form
I could be forgetting you could be forgetting he could be forgetting we could be forgetting you could be forgetting they could be forgetting
Perfect
I could have forgotten you could have forgotten he could have forgotten we could have forgotten you could have forgotten they could have forgotten
V-ing perfect
I could have been forgetting you could have been forgetting he could have been forgetting we could have been forgetting you could have been forgetting they could have been forgetting
Negation
Simple form
I could not forget you could not forget he could not forget we could not forget you could not forget they could not forget
V-ing form
I could not be forgetting you could not be forgetting he could not be forgetting we could not be forgetting you could not be forgetting they could not be forgetting
Perfect
I could not have forgotten you could not have forgotten he could not have forgotten we could not have forgotten you could not have forgotten they could not have forgotten
V-ing perfect
I could not have been forgetting you could not have been forgetting he could not have been forgetting we could not have been forgetting you could not have been forgetting they could not have been forgetting
Interrogative form
Simple form
could I forget? could you forget? could he forget? could we forget? could you forget? could they forget?
V-ing form
could I be forgetting? could you be forgetting? could he be forgetting? could we be forgetting? could you be forgetting? could they be forgetting?
Perfect
could I have forgotten? could you have forgotten? could he have forgotten? could we have forgotten? could you have forgotten? could they have forgotten?
V-ing perfect
could I have been forgetting? could you have been forgetting? could he have been forgetting? could we have been forgetting? could you have been forgetting? could they have been forgetting?
Interro-negative form
Simple form
could I not forget? could you not forget? could he not forget? could we not forget? could you not forget? could they not forget?
V-ing form
could I not be forgetting? could you not be forgetting? could he not be forgetting? could we not be forgetting? could you not be forgetting? could they not be forgetting?
Perfect
could I not have forgotten? could you not have forgotten? could he not have forgotten? could we not have forgotten? could you not have forgotten? could they not have forgotten?
V-ing perfect
could I not have been forgetting? could you not have been forgetting? could he not have been forgetting? could we not have been forgetting? could you not have been forgetting? could they not have been forgetting?