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