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