English verb conjugation
COULD UNDERSIGN

Regular verb: undersign - undersigned - undersigned

Affirmation

Simple form	V-ing form
I could undersign you could undersign he could undersign we could undersign you could undersign they could undersign	I could be undersigning you could be undersigning he could be undersigning we could be undersigning you could be undersigning they could be undersigning
Perfect	V-ing perfect
I could have undersigned you could have undersigned he could have undersigned we could have undersigned you could have undersigned they could have undersigned	I could have been undersigning you could have been undersigning he could have been undersigning we could have been undersigning you could have been undersigning they could have been undersigning

Negation

Simple form	V-ing form
I could not undersign you could not undersign he could not undersign we could not undersign you could not undersign they could not undersign	I could not be undersigning you could not be undersigning he could not be undersigning we could not be undersigning you could not be undersigning they could not be undersigning
Perfect	V-ing perfect
I could not have undersigned you could not have undersigned he could not have undersigned we could not have undersigned you could not have undersigned they could not have undersigned	I could not have been undersigning you could not have been undersigning he could not have been undersigning we could not have been undersigning you could not have been undersigning they could not have been undersigning

Interrogative form

Simple form	V-ing form
could I undersign? could you undersign? could he undersign? could we undersign? could you undersign? could they undersign?	could I be undersigning? could you be undersigning? could he be undersigning? could we be undersigning? could you be undersigning? could they be undersigning?
Perfect	V-ing perfect
could I have undersigned? could you have undersigned? could he have undersigned? could we have undersigned? could you have undersigned? could they have undersigned?	could I have been undersigning? could you have been undersigning? could he have been undersigning? could we have been undersigning? could you have been undersigning? could they have been undersigning?

Interro-negative form

Simple form	V-ing form
could I not undersign? could you not undersign? could he not undersign? could we not undersign? could you not undersign? could they not undersign?	could I not be undersigning? could you not be undersigning? could he not be undersigning? could we not be undersigning? could you not be undersigning? could they not be undersigning?
Perfect	V-ing perfect
could I not have undersigned? could you not have undersigned? could he not have undersigned? could we not have undersigned? could you not have undersigned? could they not have undersigned?	could I not have been undersigning? could you not have been undersigning? could he not have been undersigning? could we not have been undersigning? could you not have been undersigning? could they not have been undersigning?