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