I can sum you can sum he can sum we can sum you can sum they can sum
V-ing form
I can be summing you can be summing he can be summing we can be summing you can be summing they can be summing
Perfect
I can have summed you can have summed he can have summed we can have summed you can have summed they can have summed
V-ing perfect
I can have been summing you can have been summing he can have been summing we can have been summing you can have been summing they can have been summing
Negation
Simple form
I can't sum you can't sum he can't sum we can't sum you can't sum they can't sum
V-ing form
I can't be summing you can't be summing he can't be summing we can't be summing you can't be summing they can't be summing
Perfect
I can't have summed you can't have summed he can't have summed we can't have summed you can't have summed they can't have summed
V-ing perfect
I can't have been summing you can't have been summing he can't have been summing we can't have been summing you can't have been summing they can't have been summing
Interrogative form
Simple form
can I sum? can you sum? can he sum? can we sum? can you sum? can they sum?
V-ing form
can I be summing? can you be summing? can he be summing? can we be summing? can you be summing? can they be summing?
Perfect
can I have summed? can you have summed? can he have summed? can we have summed? can you have summed? can they have summed?
V-ing perfect
can I have been summing? can you have been summing? can he have been summing? can we have been summing? can you have been summing? can they have been summing?
Interro-negative form
Simple form
can't I sum? can't you sum? can't he sum? can't we sum? can't you sum? can't they sum?
V-ing form
can't I be summing? can't you be summing? can't he be summing? can't we be summing? can't you be summing? can't they be summing?
Perfect
can't I have summed? can't you have summed? can't he have summed? can't we have summed? can't you have summed? can't they have summed?
V-ing perfect
can't I have been summing? can't you have been summing? can't he have been summing? can't we have been summing? can't you have been summing? can't they have been summing?