could register
Regular verb: register - registered- registered

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could register
you could register
she could register
we could register
you could register
they could register 	I could be registering
you could be registering
she could be registering
we could be registering
you could be registering
they could be registering	I could have registered
you could have registered
she could have registered
we could have registered
you could have registered
they could have registered	I could have been registering
you could have been registering
she could have been registering
we could have been registering
you could have been registering
they could have been registering	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not register
you could not register
she could not register
we could not register
you could not register
they could not register 	I could not be registering
you could not be registering
she could not be registering
we could not be registering
you could not be registering
they could not be registering	I could not have registered
you could not have registered
she could not have registered
we could not have registered
you could not have registered
they could not have registered	I could not have been registering
you could not have been registering
she could not have been registering
we could not have been registering
you could not have been registering
they could not have been registering	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I register?
could you register?
could she register?
could we register?
could you register?
could they register? 	could I be registering?
could you be registering?
could she be registering?
could we be registering?
could you be registering?
could they be registering? 	could I have registered?
could you have registered?
could she have registered?
could we have registered?
could you have registered?
could they have registered? 	could I have been registering?
could you have been registering?
could she have been registering?
could we have been registering?
could you have been registering?
could they have been registering? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not register?
could you not register?
could she not register?
could we not register?
could you not register?
could they not register? 	could I not be registering?
could you not be registering?
could she not be registering?
could we not be registering?
could you not be registering?
could they not be registering? 	could I not have registered?
could you not have registered?
could she not have registered?
could we not have registered?
could you not have registered?
could they not have registered? 	could I not have been registering?
could you not have been registering?
could she not have been registering?
could we not have been registering?
could you not have been registering?
could they not have been registering?