I can register you can register he can register we can register you can register they can register
V-ing form
I can be registering you can be registering he can be registering we can be registering you can be registering they can be registering
Perfect
I can have registered you can have registered he can have registered we can have registered you can have registered they can have registered
V-ing perfect
I can have been registering you can have been registering he can have been registering we can have been registering you can have been registering they can have been registering
Negation
Simple form
I can't register you can't register he can't register we can't register you can't register they can't register
V-ing form
I can't be registering you can't be registering he can't be registering we can't be registering you can't be registering they can't be registering
Perfect
I can't have registered you can't have registered he can't have registered we can't have registered you can't have registered they can't have registered
V-ing perfect
I can't have been registering you can't have been registering he can't have been registering we can't have been registering you can't have been registering they can't have been registering
Interrogative form
Simple form
can I register? can you register? can he register? can we register? can you register? can they register?
V-ing form
can I be registering? can you be registering? can he be registering? can we be registering? can you be registering? can they be registering?
Perfect
can I have registered? can you have registered? can he have registered? can we have registered? can you have registered? can they have registered?
V-ing perfect
can I have been registering? can you have been registering? can he have been registering? can we have been registering? can you have been registering? can they have been registering?
Interro-negative form
Simple form
can't I register? can't you register? can't he register? can't we register? can't you register? can't they register?
V-ing form
can't I be registering? can't you be registering? can't he be registering? can't we be registering? can't you be registering? can't they be registering?
Perfect
can't I have registered? can't you have registered? can't he have registered? can't we have registered? can't you have registered? can't they have registered?
V-ing perfect
can't I have been registering? can't you have been registering? can't he have been registering? can't we have been registering? can't you have been registering? can't they have been registering?