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