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