English verb conjugation
COULD CHECK

Regular verb: check - checked - checked

Affirmation

Simple form	V-ing form
I could check you could check he could check we could check you could check they could check	I could be checking you could be checking he could be checking we could be checking you could be checking they could be checking
Perfect	V-ing perfect
I could have checked you could have checked he could have checked we could have checked you could have checked they could have checked	I could have been checking you could have been checking he could have been checking we could have been checking you could have been checking they could have been checking

Negation

Simple form	V-ing form
I couldn't check you couldn't check he couldn't check we couldn't check you couldn't check they couldn't check	I couldn't be checking you couldn't be checking he couldn't be checking we couldn't be checking you couldn't be checking they couldn't be checking
Perfect	V-ing perfect
I couldn't have checked you couldn't have checked he couldn't have checked we couldn't have checked you couldn't have checked they couldn't have checked	I couldn't have been checking you couldn't have been checking he couldn't have been checking we couldn't have been checking you couldn't have been checking they couldn't have been checking

Interrogative form

Simple form	V-ing form
could I check? could you check? could he check? could we check? could you check? could they check?	could I be checking? could you be checking? could he be checking? could we be checking? could you be checking? could they be checking?
Perfect	V-ing perfect
could I have checked? could you have checked? could he have checked? could we have checked? could you have checked? could they have checked?	could I have been checking? could you have been checking? could he have been checking? could we have been checking? could you have been checking? could they have been checking?

Interro-negative form

Simple form	V-ing form
couldn't I check? couldn't you check? couldn't he check? couldn't we check? couldn't you check? couldn't they check?	couldn't I be checking? couldn't you be checking? couldn't he be checking? couldn't we be checking? couldn't you be checking? couldn't they be checking?
Perfect	V-ing perfect
couldn't I have checked? couldn't you have checked? couldn't he have checked? couldn't we have checked? couldn't you have checked? couldn't they have checked?	couldn't I have been checking? couldn't you have been checking? couldn't he have been checking? couldn't we have been checking? couldn't you have been checking? couldn't they have been checking?