I could write you could write she could write we could write you could write they could write
V-ing form
I could be writing you could be writing she could be writing we could be writing you could be writing they could be writing
Perfect
I could have written you could have written she could have written we could have written you could have written they could have written
V-ing perfect
I could have been writing you could have been writing she could have been writing we could have been writing you could have been writing they could have been writing
Negation
Simple form
I couldn't write you couldn't write she couldn't write we couldn't write you couldn't write they couldn't write
V-ing form
I couldn't be writing you couldn't be writing she couldn't be writing we couldn't be writing you couldn't be writing they couldn't be writing
Perfect
I couldn't have written you couldn't have written she couldn't have written we couldn't have written you couldn't have written they couldn't have written
V-ing perfect
I couldn't have been writing you couldn't have been writing she couldn't have been writing we couldn't have been writing you couldn't have been writing they couldn't have been writing
Interrogative form
Simple form
could I write? could you write? could she write? could we write? could you write? could they write?
V-ing form
could I be writing? could you be writing? could she be writing? could we be writing? could you be writing? could they be writing?
Perfect
could I have written? could you have written? could she have written? could we have written? could you have written? could they have written?
V-ing perfect
could I have been writing? could you have been writing? could she have been writing? could we have been writing? could you have been writing? could they have been writing?
Interro-negative form
Simple form
couldn't I write? couldn't you write? couldn't she write? couldn't we write? couldn't you write? couldn't they write?
V-ing form
couldn't I be writing? couldn't you be writing? couldn't she be writing? couldn't we be writing? couldn't you be writing? couldn't they be writing?
Perfect
couldn't I have written? couldn't you have written? couldn't she have written? couldn't we have written? couldn't you have written? couldn't they have written?
V-ing perfect
couldn't I have been writing? couldn't you have been writing? couldn't she have been writing? couldn't we have been writing? couldn't you have been writing? couldn't they have been writing?