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