I could retire you could retire he could retire we could retire you could retire they could retire
V-ing form
I could be retiring you could be retiring he could be retiring we could be retiring you could be retiring they could be retiring
Perfect
I could have retired you could have retired he could have retired we could have retired you could have retired they could have retired
V-ing perfect
I could have been retiring you could have been retiring he could have been retiring we could have been retiring you could have been retiring they could have been retiring
Negation
Simple form
I could not retire you could not retire he could not retire we could not retire you could not retire they could not retire
V-ing form
I could not be retiring you could not be retiring he could not be retiring we could not be retiring you could not be retiring they could not be retiring
Perfect
I could not have retired you could not have retired he could not have retired we could not have retired you could not have retired they could not have retired
V-ing perfect
I could not have been retiring you could not have been retiring he could not have been retiring we could not have been retiring you could not have been retiring they could not have been retiring
Interrogative form
Simple form
could I retire? could you retire? could he retire? could we retire? could you retire? could they retire?
V-ing form
could I be retiring? could you be retiring? could he be retiring? could we be retiring? could you be retiring? could they be retiring?
Perfect
could I have retired? could you have retired? could he have retired? could we have retired? could you have retired? could they have retired?
V-ing perfect
could I have been retiring? could you have been retiring? could he have been retiring? could we have been retiring? could you have been retiring? could they have been retiring?
Interro-negative form
Simple form
could I not retire? could you not retire? could he not retire? could we not retire? could you not retire? could they not retire?
V-ing form
could I not be retiring? could you not be retiring? could he not be retiring? could we not be retiring? could you not be retiring? could they not be retiring?
Perfect
could I not have retired? could you not have retired? could he not have retired? could we not have retired? could you not have retired? could they not have retired?
V-ing perfect
could I not have been retiring? could you not have been retiring? could he not have been retiring? could we not have been retiring? could you not have been retiring? could they not have been retiring?