I could file you could file she could file we could file you could file they could file
V-ing form
I could be filing you could be filing she could be filing we could be filing you could be filing they could be filing
Perfect
I could have filed you could have filed she could have filed we could have filed you could have filed they could have filed
V-ing perfect
I could have been filing you could have been filing she could have been filing we could have been filing you could have been filing they could have been filing
Negation
Simple form
I could not file you could not file she could not file we could not file you could not file they could not file
V-ing form
I could not be filing you could not be filing she could not be filing we could not be filing you could not be filing they could not be filing
Perfect
I could not have filed you could not have filed she could not have filed we could not have filed you could not have filed they could not have filed
V-ing perfect
I could not have been filing you could not have been filing she could not have been filing we could not have been filing you could not have been filing they could not have been filing
Interrogative form
Simple form
could I file? could you file? could she file? could we file? could you file? could they file?
V-ing form
could I be filing? could you be filing? could she be filing? could we be filing? could you be filing? could they be filing?
Perfect
could I have filed? could you have filed? could she have filed? could we have filed? could you have filed? could they have filed?
V-ing perfect
could I have been filing? could you have been filing? could she have been filing? could we have been filing? could you have been filing? could they have been filing?
Interro-negative form
Simple form
could I not file? could you not file? could she not file? could we not file? could you not file? could they not file?
V-ing form
could I not be filing? could you not be filing? could she not be filing? could we not be filing? could you not be filing? could they not be filing?
Perfect
could I not have filed? could you not have filed? could she not have filed? could we not have filed? could you not have filed? could they not have filed?
V-ing perfect
could I not have been filing? could you not have been filing? could she not have been filing? could we not have been filing? could you not have been filing? could they not have been filing?