I can avouch you can avouch he can avouch we can avouch you can avouch they can avouch
V-ing form
I can be avouching you can be avouching he can be avouching we can be avouching you can be avouching they can be avouching
Perfect
I can have avouched you can have avouched he can have avouched we can have avouched you can have avouched they can have avouched
V-ing perfect
I can have been avouching you can have been avouching he can have been avouching we can have been avouching you can have been avouching they can have been avouching
Negation
Simple form
I cannot avouch you cannot avouch he cannot avouch we cannot avouch you cannot avouch they cannot avouch
V-ing form
I cannot be avouching you cannot be avouching he cannot be avouching we cannot be avouching you cannot be avouching they cannot be avouching
Perfect
I cannot have avouched you cannot have avouched he cannot have avouched we cannot have avouched you cannot have avouched they cannot have avouched
V-ing perfect
I cannot have been avouching you cannot have been avouching he cannot have been avouching we cannot have been avouching you cannot have been avouching they cannot have been avouching
Interrogative form
Simple form
can I avouch? can you avouch? can he avouch? can we avouch? can you avouch? can they avouch?
V-ing form
can I be avouching? can you be avouching? can he be avouching? can we be avouching? can you be avouching? can they be avouching?
Perfect
can I have avouched? can you have avouched? can he have avouched? can we have avouched? can you have avouched? can they have avouched?
V-ing perfect
can I have been avouching? can you have been avouching? can he have been avouching? can we have been avouching? can you have been avouching? can they have been avouching?
Interro-negative form
Simple form
can I not avouch? can you not avouch? can he not avouch? can we not avouch? can you not avouch? can they not avouch?
V-ing form
can I not be avouching? can you not be avouching? can he not be avouching? can we not be avouching? can you not be avouching? can they not be avouching?
Perfect
can I not have avouched? can you not have avouched? can he not have avouched? can we not have avouched? can you not have avouched? can they not have avouched?
V-ing perfect
can I not have been avouching? can you not have been avouching? can he not have been avouching? can we not have been avouching? can you not have been avouching? can they not have been avouching?