I can certify you can certify he can certify we can certify you can certify they can certify
V-ing form
I can be certifying you can be certifying he can be certifying we can be certifying you can be certifying they can be certifying
Perfect
I can have certified you can have certified he can have certified we can have certified you can have certified they can have certified
V-ing perfect
I can have been certifying you can have been certifying he can have been certifying we can have been certifying you can have been certifying they can have been certifying
Negation
Simple form
I cannot certify you cannot certify he cannot certify we cannot certify you cannot certify they cannot certify
V-ing form
I cannot be certifying you cannot be certifying he cannot be certifying we cannot be certifying you cannot be certifying they cannot be certifying
Perfect
I cannot have certified you cannot have certified he cannot have certified we cannot have certified you cannot have certified they cannot have certified
V-ing perfect
I cannot have been certifying you cannot have been certifying he cannot have been certifying we cannot have been certifying you cannot have been certifying they cannot have been certifying
Interrogative form
Simple form
can I certify? can you certify? can he certify? can we certify? can you certify? can they certify?
V-ing form
can I be certifying? can you be certifying? can he be certifying? can we be certifying? can you be certifying? can they be certifying?
Perfect
can I have certified? can you have certified? can he have certified? can we have certified? can you have certified? can they have certified?
V-ing perfect
can I have been certifying? can you have been certifying? can he have been certifying? can we have been certifying? can you have been certifying? can they have been certifying?
Interro-negative form
Simple form
can I not certify? can you not certify? can he not certify? can we not certify? can you not certify? can they not certify?
V-ing form
can I not be certifying? can you not be certifying? can he not be certifying? can we not be certifying? can you not be certifying? can they not be certifying?
Perfect
can I not have certified? can you not have certified? can he not have certified? can we not have certified? can you not have certified? can they not have certified?
V-ing perfect
can I not have been certifying? can you not have been certifying? can he not have been certifying? can we not have been certifying? can you not have been certifying? can they not have been certifying?