English verb conjugation
COULD POSTMARK

Regular verb: postmark - postmarked - postmarked

Affirmation

Simple form	V-ing form
I could postmark you could postmark he could postmark we could postmark you could postmark they could postmark	I could be postmarking you could be postmarking he could be postmarking we could be postmarking you could be postmarking they could be postmarking
Perfect	V-ing perfect
I could have postmarked you could have postmarked he could have postmarked we could have postmarked you could have postmarked they could have postmarked	I could have been postmarking you could have been postmarking he could have been postmarking we could have been postmarking you could have been postmarking they could have been postmarking

Negation

Simple form	V-ing form
I could not postmark you could not postmark he could not postmark we could not postmark you could not postmark they could not postmark	I could not be postmarking you could not be postmarking he could not be postmarking we could not be postmarking you could not be postmarking they could not be postmarking
Perfect	V-ing perfect
I could not have postmarked you could not have postmarked he could not have postmarked we could not have postmarked you could not have postmarked they could not have postmarked	I could not have been postmarking you could not have been postmarking he could not have been postmarking we could not have been postmarking you could not have been postmarking they could not have been postmarking

Interrogative form

Simple form	V-ing form
could I postmark? could you postmark? could he postmark? could we postmark? could you postmark? could they postmark?	could I be postmarking? could you be postmarking? could he be postmarking? could we be postmarking? could you be postmarking? could they be postmarking?
Perfect	V-ing perfect
could I have postmarked? could you have postmarked? could he have postmarked? could we have postmarked? could you have postmarked? could they have postmarked?	could I have been postmarking? could you have been postmarking? could he have been postmarking? could we have been postmarking? could you have been postmarking? could they have been postmarking?

Interro-negative form

Simple form	V-ing form
could I not postmark? could you not postmark? could he not postmark? could we not postmark? could you not postmark? could they not postmark?	could I not be postmarking? could you not be postmarking? could he not be postmarking? could we not be postmarking? could you not be postmarking? could they not be postmarking?
Perfect	V-ing perfect
could I not have postmarked? could you not have postmarked? could he not have postmarked? could we not have postmarked? could you not have postmarked? could they not have postmarked?	could I not have been postmarking? could you not have been postmarking? could he not have been postmarking? could we not have been postmarking? could you not have been postmarking? could they not have been postmarking?