I could say you could say she could say we could say you could say they could say
V-ing form
I could be saying you could be saying she could be saying we could be saying you could be saying they could be saying
Perfect
I could have said you could have said she 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 she 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 she 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 she 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 she 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 she 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 she say? could we say? could you say? could they say?
V-ing form
could I be saying? could you be saying? could she be saying? could we be saying? could you be saying? could they be saying?
Perfect
could I have said? could you have said? could she 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 she 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 she 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 she 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 she 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 she have been saying? couldn't we have been saying? couldn't you have been saying? couldn't they have been saying?