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