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 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	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 	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'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? 	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?