Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could pay off you could pay off he could pay off we could pay off you could pay off they could pay off
V-ing form
I could be pay offing you could be pay offing he could be pay offing we could be pay offing you could be pay offing they could be pay offing
Perfect
I could have pay offed you could have pay offed he could have pay offed we could have pay offed you could have pay offed they could have pay offed
V-ing perfect
I could have been pay offing you could have been pay offing he could have been pay offing we could have been pay offing you could have been pay offing they could have been pay offing
Negation
Simple form
I couldn't pay off you couldn't pay off he couldn't pay off we couldn't pay off you couldn't pay off they couldn't pay off
V-ing form
I couldn't be pay offing you couldn't be pay offing he couldn't be pay offing we couldn't be pay offing you couldn't be pay offing they couldn't be pay offing
Perfect
I couldn't have pay offed you couldn't have pay offed he couldn't have pay offed we couldn't have pay offed you couldn't have pay offed they couldn't have pay offed
V-ing perfect
I couldn't have been pay offing you couldn't have been pay offing he couldn't have been pay offing we couldn't have been pay offing you couldn't have been pay offing they couldn't have been pay offing
Interrogative form
Simple form
could I pay off? could you pay off? could he pay off? could we pay off? could you pay off? could they pay off?
V-ing form
could I be pay offing? could you be pay offing? could he be pay offing? could we be pay offing? could you be pay offing? could they be pay offing?
Perfect
could I have pay offed? could you have pay offed? could he have pay offed? could we have pay offed? could you have pay offed? could they have pay offed?
V-ing perfect
could I have been pay offing? could you have been pay offing? could he have been pay offing? could we have been pay offing? could you have been pay offing? could they have been pay offing?
Interro-negative form
Simple form
couldn't I pay off? couldn't you pay off? couldn't he pay off? couldn't we pay off? couldn't you pay off? couldn't they pay off?
V-ing form
couldn't I be pay offing? couldn't you be pay offing? couldn't he be pay offing? couldn't we be pay offing? couldn't you be pay offing? couldn't they be pay offing?
Perfect
couldn't I have pay offed? couldn't you have pay offed? couldn't he have pay offed? couldn't we have pay offed? couldn't you have pay offed? couldn't they have pay offed?
V-ing perfect
couldn't I have been pay offing? couldn't you have been pay offing? couldn't he have been pay offing? couldn't we have been pay offing? couldn't you have been pay offing? couldn't they have been pay offing?