I could overfill you could overfill he could overfill we could overfill you could overfill they could overfill
V-ing form
I could be overfilling you could be overfilling he could be overfilling we could be overfilling you could be overfilling they could be overfilling
Perfect
I could have overfilled you could have overfilled he could have overfilled we could have overfilled you could have overfilled they could have overfilled
V-ing perfect
I could have been overfilling you could have been overfilling he could have been overfilling we could have been overfilling you could have been overfilling they could have been overfilling
Negation
Simple form
I couldn't overfill you couldn't overfill he couldn't overfill we couldn't overfill you couldn't overfill they couldn't overfill
V-ing form
I couldn't be overfilling you couldn't be overfilling he couldn't be overfilling we couldn't be overfilling you couldn't be overfilling they couldn't be overfilling
Perfect
I couldn't have overfilled you couldn't have overfilled he couldn't have overfilled we couldn't have overfilled you couldn't have overfilled they couldn't have overfilled
V-ing perfect
I couldn't have been overfilling you couldn't have been overfilling he couldn't have been overfilling we couldn't have been overfilling you couldn't have been overfilling they couldn't have been overfilling
Interrogative form
Simple form
could I overfill? could you overfill? could he overfill? could we overfill? could you overfill? could they overfill?
V-ing form
could I be overfilling? could you be overfilling? could he be overfilling? could we be overfilling? could you be overfilling? could they be overfilling?
Perfect
could I have overfilled? could you have overfilled? could he have overfilled? could we have overfilled? could you have overfilled? could they have overfilled?
V-ing perfect
could I have been overfilling? could you have been overfilling? could he have been overfilling? could we have been overfilling? could you have been overfilling? could they have been overfilling?
Interro-negative form
Simple form
couldn't I overfill? couldn't you overfill? couldn't he overfill? couldn't we overfill? couldn't you overfill? couldn't they overfill?
V-ing form
couldn't I be overfilling? couldn't you be overfilling? couldn't he be overfilling? couldn't we be overfilling? couldn't you be overfilling? couldn't they be overfilling?
Perfect
couldn't I have overfilled? couldn't you have overfilled? couldn't he have overfilled? couldn't we have overfilled? couldn't you have overfilled? couldn't they have overfilled?
V-ing perfect
couldn't I have been overfilling? couldn't you have been overfilling? couldn't he have been overfilling? couldn't we have been overfilling? couldn't you have been overfilling? couldn't they have been overfilling?