I could countersign you could countersign he could countersign we could countersign you could countersign they could countersign
V-ing form
I could be countersigning you could be countersigning he could be countersigning we could be countersigning you could be countersigning they could be countersigning
Perfect
I could have countersigned you could have countersigned he could have countersigned we could have countersigned you could have countersigned they could have countersigned
V-ing perfect
I could have been countersigning you could have been countersigning he could have been countersigning we could have been countersigning you could have been countersigning they could have been countersigning
Negation
Simple form
I couldn't countersign you couldn't countersign he couldn't countersign we couldn't countersign you couldn't countersign they couldn't countersign
V-ing form
I couldn't be countersigning you couldn't be countersigning he couldn't be countersigning we couldn't be countersigning you couldn't be countersigning they couldn't be countersigning
Perfect
I couldn't have countersigned you couldn't have countersigned he couldn't have countersigned we couldn't have countersigned you couldn't have countersigned they couldn't have countersigned
V-ing perfect
I couldn't have been countersigning you couldn't have been countersigning he couldn't have been countersigning we couldn't have been countersigning you couldn't have been countersigning they couldn't have been countersigning
Interrogative form
Simple form
could I countersign? could you countersign? could he countersign? could we countersign? could you countersign? could they countersign?
V-ing form
could I be countersigning? could you be countersigning? could he be countersigning? could we be countersigning? could you be countersigning? could they be countersigning?
Perfect
could I have countersigned? could you have countersigned? could he have countersigned? could we have countersigned? could you have countersigned? could they have countersigned?
V-ing perfect
could I have been countersigning? could you have been countersigning? could he have been countersigning? could we have been countersigning? could you have been countersigning? could they have been countersigning?
Interro-negative form
Simple form
couldn't I countersign? couldn't you countersign? couldn't he countersign? couldn't we countersign? couldn't you countersign? couldn't they countersign?
V-ing form
couldn't I be countersigning? couldn't you be countersigning? couldn't he be countersigning? couldn't we be countersigning? couldn't you be countersigning? couldn't they be countersigning?
Perfect
couldn't I have countersigned? couldn't you have countersigned? couldn't he have countersigned? couldn't we have countersigned? couldn't you have countersigned? couldn't they have countersigned?
V-ing perfect
couldn't I have been countersigning? couldn't you have been countersigning? couldn't he have been countersigning? couldn't we have been countersigning? couldn't you have been countersigning? couldn't they have been countersigning?