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 couldn't file you couldn't file she couldn't file we couldn't file you couldn't file they couldn't file
V-ing form
I couldn't be filing you couldn't be filing she couldn't be filing we couldn't be filing you couldn't be filing they couldn't be filing
Perfect
I couldn't have filed you couldn't have filed she couldn't have filed we couldn't have filed you couldn't have filed they couldn't have filed
V-ing perfect
I couldn't have been filing you couldn't have been filing she couldn't have been filing we couldn't have been filing you couldn't have been filing they couldn't 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
couldn't I file? couldn't you file? couldn't she file? couldn't we file? couldn't you file? couldn't they file?
V-ing form
couldn't I be filing? couldn't you be filing? couldn't she be filing? couldn't we be filing? couldn't you be filing? couldn't they be filing?
Perfect
couldn't I have filed? couldn't you have filed? couldn't she have filed? couldn't we have filed? couldn't you have filed? couldn't they have filed?
V-ing perfect
couldn't I have been filing? couldn't you have been filing? couldn't she have been filing? couldn't we have been filing? couldn't you have been filing? couldn't they have been filing?