English verb conjugation
COULD START

Regular verb: start - started - started

Affirmation

Simple form	V-ing form
I could start you could start he could start we could start you could start they could start	I could be starting you could be starting he could be starting we could be starting you could be starting they could be starting
Perfect	V-ing perfect
I could have started you could have started he could have started we could have started you could have started they could have started	I could have been starting you could have been starting he could have been starting we could have been starting you could have been starting they could have been starting

Negation

Simple form	V-ing form
I could not start you could not start he could not start we could not start you could not start they could not start	I could not be starting you could not be starting he could not be starting we could not be starting you could not be starting they could not be starting
Perfect	V-ing perfect
I could not have started you could not have started he could not have started we could not have started you could not have started they could not have started	I could not have been starting you could not have been starting he could not have been starting we could not have been starting you could not have been starting they could not have been starting

Interrogative form

Simple form	V-ing form
could I start? could you start? could he start? could we start? could you start? could they start?	could I be starting? could you be starting? could he be starting? could we be starting? could you be starting? could they be starting?
Perfect	V-ing perfect
could I have started? could you have started? could he have started? could we have started? could you have started? could they have started?	could I have been starting? could you have been starting? could he have been starting? could we have been starting? could you have been starting? could they have been starting?

Interro-negative form

Simple form	V-ing form
could I not start? could you not start? could he not start? could we not start? could you not start? could they not start?	could I not be starting? could you not be starting? could he not be starting? could we not be starting? could you not be starting? could they not be starting?
Perfect	V-ing perfect
could I not have started? could you not have started? could he not have started? could we not have started? could you not have started? could they not have started?	could I not have been starting? could you not have been starting? could he not have been starting? could we not have been starting? could you not have been starting? could they not have been starting?