English verb conjugation
COULD POSTFIX

Regular verb: postfix - postfixed - postfixed

Affirmation

Simple form	V-ing form
I could postfix you could postfix he could postfix we could postfix you could postfix they could postfix	I could be postfixing you could be postfixing he could be postfixing we could be postfixing you could be postfixing they could be postfixing
Perfect	V-ing perfect
I could have postfixed you could have postfixed he could have postfixed we could have postfixed you could have postfixed they could have postfixed	I could have been postfixing you could have been postfixing he could have been postfixing we could have been postfixing you could have been postfixing they could have been postfixing

Negation

Simple form	V-ing form
I could not postfix you could not postfix he could not postfix we could not postfix you could not postfix they could not postfix	I could not be postfixing you could not be postfixing he could not be postfixing we could not be postfixing you could not be postfixing they could not be postfixing
Perfect	V-ing perfect
I could not have postfixed you could not have postfixed he could not have postfixed we could not have postfixed you could not have postfixed they could not have postfixed	I could not have been postfixing you could not have been postfixing he could not have been postfixing we could not have been postfixing you could not have been postfixing they could not have been postfixing

Interrogative form

Simple form	V-ing form
could I postfix? could you postfix? could he postfix? could we postfix? could you postfix? could they postfix?	could I be postfixing? could you be postfixing? could he be postfixing? could we be postfixing? could you be postfixing? could they be postfixing?
Perfect	V-ing perfect
could I have postfixed? could you have postfixed? could he have postfixed? could we have postfixed? could you have postfixed? could they have postfixed?	could I have been postfixing? could you have been postfixing? could he have been postfixing? could we have been postfixing? could you have been postfixing? could they have been postfixing?

Interro-negative form

Simple form	V-ing form
could I not postfix? could you not postfix? could he not postfix? could we not postfix? could you not postfix? could they not postfix?	could I not be postfixing? could you not be postfixing? could he not be postfixing? could we not be postfixing? could you not be postfixing? could they not be postfixing?
Perfect	V-ing perfect
could I not have postfixed? could you not have postfixed? could he not have postfixed? could we not have postfixed? could you not have postfixed? could they not have postfixed?	could I not have been postfixing? could you not have been postfixing? could he not have been postfixing? could we not have been postfixing? could you not have been postfixing? could they not have been postfixing?