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