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