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