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