can countersign
Regular verb: countersign - countersigned- countersigned

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
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	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 	Perfect 	V-ing perfect 	
I cannot countersign
you cannot countersign
he cannot countersign
we cannot countersign
you cannot countersign
they cannot countersign 	I cannot be countersigning
you cannot be countersigning
he cannot be countersigning
we cannot be countersigning
you cannot be countersigning
they cannot be countersigning	I cannot have countersigned
you cannot have countersigned
he cannot have countersigned
we cannot have countersigned
you cannot have countersigned
they cannot have countersigned	I cannot have been countersigning
you cannot have been countersigning
he cannot have been countersigning
we cannot have been countersigning
you cannot have been countersigning
they cannot have been countersigning	

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