I could invalidate you could invalidate she could invalidate we could invalidate you could invalidate they could invalidate
V-ing form
I could be invalidating you could be invalidating she could be invalidating we could be invalidating you could be invalidating they could be invalidating
Perfect
I could have invalidated you could have invalidated she could have invalidated we could have invalidated you could have invalidated they could have invalidated
V-ing perfect
I could have been invalidating you could have been invalidating she could have been invalidating we could have been invalidating you could have been invalidating they could have been invalidating
Negation
Simple form
I couldn't invalidate you couldn't invalidate she couldn't invalidate we couldn't invalidate you couldn't invalidate they couldn't invalidate
V-ing form
I couldn't be invalidating you couldn't be invalidating she couldn't be invalidating we couldn't be invalidating you couldn't be invalidating they couldn't be invalidating
Perfect
I couldn't have invalidated you couldn't have invalidated she couldn't have invalidated we couldn't have invalidated you couldn't have invalidated they couldn't have invalidated
V-ing perfect
I couldn't have been invalidating you couldn't have been invalidating she couldn't have been invalidating we couldn't have been invalidating you couldn't have been invalidating they couldn't have been invalidating
Interrogative form
Simple form
could I invalidate? could you invalidate? could she invalidate? could we invalidate? could you invalidate? could they invalidate?
V-ing form
could I be invalidating? could you be invalidating? could she be invalidating? could we be invalidating? could you be invalidating? could they be invalidating?
Perfect
could I have invalidated? could you have invalidated? could she have invalidated? could we have invalidated? could you have invalidated? could they have invalidated?
V-ing perfect
could I have been invalidating? could you have been invalidating? could she have been invalidating? could we have been invalidating? could you have been invalidating? could they have been invalidating?
Interro-negative form
Simple form
couldn't I invalidate? couldn't you invalidate? couldn't she invalidate? couldn't we invalidate? couldn't you invalidate? couldn't they invalidate?
V-ing form
couldn't I be invalidating? couldn't you be invalidating? couldn't she be invalidating? couldn't we be invalidating? couldn't you be invalidating? couldn't they be invalidating?
Perfect
couldn't I have invalidated? couldn't you have invalidated? couldn't she have invalidated? couldn't we have invalidated? couldn't you have invalidated? couldn't they have invalidated?
V-ing perfect
couldn't I have been invalidating? couldn't you have been invalidating? couldn't she have been invalidating? couldn't we have been invalidating? couldn't you have been invalidating? couldn't they have been invalidating?