English verb conjugation
CAN COUNTERSIGN

Regular verb: countersign - countersigned - countersigned

Affirmation

Simple form	V-ing form
I can countersign you can countersign he can countersign we can countersign you can countersign they can countersign	I can be countersigning you can be countersigning he can be countersigning we can be countersigning you can be countersigning they can be countersigning
Perfect	V-ing perfect
I can have countersigned you can have countersigned he can have countersigned we can have countersigned you can have countersigned they can have countersigned	I can have been countersigning you can have been countersigning he can have been countersigning we can have been countersigning you can have been countersigning they can have been countersigning

Negation

Simple form	V-ing form
I can't countersign you can't countersign he can't countersign we can't countersign you can't countersign they can't countersign	I can't be countersigning you can't be countersigning he can't be countersigning we can't be countersigning you can't be countersigning they can't be countersigning
Perfect	V-ing perfect
I can't have countersigned you can't have countersigned he can't have countersigned we can't have countersigned you can't have countersigned they can't have countersigned	I can't have been countersigning you can't have been countersigning he can't have been countersigning we can't have been countersigning you can't have been countersigning they can't have been countersigning

Interrogative form

Simple form	V-ing form
can I countersign? can you countersign? can he countersign? can we countersign? can you countersign? can they countersign?	can I be countersigning? can you be countersigning? can he be countersigning? can we be countersigning? can you be countersigning? can they be countersigning?
Perfect	V-ing perfect
can I have countersigned? can you have countersigned? can he have countersigned? can we have countersigned? can you have countersigned? can they have countersigned?	can I have been countersigning? can you have been countersigning? can he have been countersigning? can we have been countersigning? can you have been countersigning? can they have been countersigning?

Interro-negative form

Simple form	V-ing form
can't I countersign? can't you countersign? can't he countersign? can't we countersign? can't you countersign? can't they countersign?	can't I be countersigning? can't you be countersigning? can't he be countersigning? can't we be countersigning? can't you be countersigning? can't they be countersigning?
Perfect	V-ing perfect
can't I have countersigned? can't you have countersigned? can't he have countersigned? can't we have countersigned? can't you have countersigned? can't they have countersigned?	can't I have been countersigning? can't you have been countersigning? can't he have been countersigning? can't we have been countersigning? can't you have been countersigning? can't they have been countersigning?