Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could stay up you could stay up she could stay up we could stay up you could stay up they could stay up
V-ing form
I could be stay uping you could be stay uping she could be stay uping we could be stay uping you could be stay uping they could be stay uping
Perfect
I could have stay uped you could have stay uped she could have stay uped we could have stay uped you could have stay uped they could have stay uped
V-ing perfect
I could have been stay uping you could have been stay uping she could have been stay uping we could have been stay uping you could have been stay uping they could have been stay uping
Negation
Simple form
I couldn't stay up you couldn't stay up she couldn't stay up we couldn't stay up you couldn't stay up they couldn't stay up
V-ing form
I couldn't be stay uping you couldn't be stay uping she couldn't be stay uping we couldn't be stay uping you couldn't be stay uping they couldn't be stay uping
Perfect
I couldn't have stay uped you couldn't have stay uped she couldn't have stay uped we couldn't have stay uped you couldn't have stay uped they couldn't have stay uped
V-ing perfect
I couldn't have been stay uping you couldn't have been stay uping she couldn't have been stay uping we couldn't have been stay uping you couldn't have been stay uping they couldn't have been stay uping
Interrogative form
Simple form
could I stay up? could you stay up? could she stay up? could we stay up? could you stay up? could they stay up?
V-ing form
could I be stay uping? could you be stay uping? could she be stay uping? could we be stay uping? could you be stay uping? could they be stay uping?
Perfect
could I have stay uped? could you have stay uped? could she have stay uped? could we have stay uped? could you have stay uped? could they have stay uped?
V-ing perfect
could I have been stay uping? could you have been stay uping? could she have been stay uping? could we have been stay uping? could you have been stay uping? could they have been stay uping?
Interro-negative form
Simple form
couldn't I stay up? couldn't you stay up? couldn't she stay up? couldn't we stay up? couldn't you stay up? couldn't they stay up?
V-ing form
couldn't I be stay uping? couldn't you be stay uping? couldn't she be stay uping? couldn't we be stay uping? couldn't you be stay uping? couldn't they be stay uping?
Perfect
couldn't I have stay uped? couldn't you have stay uped? couldn't she have stay uped? couldn't we have stay uped? couldn't you have stay uped? couldn't they have stay uped?
V-ing perfect
couldn't I have been stay uping? couldn't you have been stay uping? couldn't she have been stay uping? couldn't we have been stay uping? couldn't you have been stay uping? couldn't they have been stay uping?