English verb conjugation
COULD INVALIDATE

Regular verb: invalidate - invalidated - invalidated

Affirmation

Simple form	V-ing form
I could invalidate you could invalidate he could invalidate we could invalidate you could invalidate they could invalidate	I could be invalidating you could be invalidating he could be invalidating we could be invalidating you could be invalidating they could be invalidating
Perfect	V-ing perfect
I could have invalidated you could have invalidated he could have invalidated we could have invalidated you could have invalidated they could have invalidated	I could have been invalidating you could have been invalidating he could have been invalidating we could have been invalidating you could have been invalidating they could have been invalidating

Negation

Simple form	V-ing form
I couldn't invalidate you couldn't invalidate he couldn't invalidate we couldn't invalidate you couldn't invalidate they couldn't invalidate	I couldn't be invalidating you couldn't be invalidating he couldn't be invalidating we couldn't be invalidating you couldn't be invalidating they couldn't be invalidating
Perfect	V-ing perfect
I couldn't have invalidated you couldn't have invalidated he couldn't have invalidated we couldn't have invalidated you couldn't have invalidated they couldn't have invalidated	I couldn't have been invalidating you couldn't have been invalidating he 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	V-ing form
could I invalidate? could you invalidate? could he invalidate? could we invalidate? could you invalidate? could they invalidate?	could I be invalidating? could you be invalidating? could he be invalidating? could we be invalidating? could you be invalidating? could they be invalidating?
Perfect	V-ing perfect
could I have invalidated? could you have invalidated? could he have invalidated? could we have invalidated? could you have invalidated? could they have invalidated?	could I have been invalidating? could you have been invalidating? could he have been invalidating? could we have been invalidating? could you have been invalidating? could they have been invalidating?

Interro-negative form

Simple form	V-ing form
couldn't I invalidate? couldn't you invalidate? couldn't he invalidate? couldn't we invalidate? couldn't you invalidate? couldn't they invalidate?	couldn't I be invalidating? couldn't you be invalidating? couldn't he be invalidating? couldn't we be invalidating? couldn't you be invalidating? couldn't they be invalidating?
Perfect	V-ing perfect
couldn't I have invalidated? couldn't you have invalidated? couldn't he have invalidated? couldn't we have invalidated? couldn't you have invalidated? couldn't they have invalidated?	couldn't I have been invalidating? couldn't you have been invalidating? couldn't he have been invalidating? couldn't we have been invalidating? couldn't you have been invalidating? couldn't they have been invalidating?