I may back you may back she may back we may back you may back they may back
V-ing form
I may be backing you may be backing she may be backing we may be backing you may be backing they may be backing
Perfect
I may have backed you may have backed she may have backed we may have backed you may have backed they may have backed
V-ing perfect
I may have been backing you may have been backing she may have been backing we may have been backing you may have been backing they may have been backing
Negation
Simple form
I mayn't back you mayn't back she mayn't back we mayn't back you mayn't back they mayn't back
V-ing form
I mayn't be backing you mayn't be backing she mayn't be backing we mayn't be backing you mayn't be backing they mayn't be backing
Perfect
I mayn't have backed you mayn't have backed she mayn't have backed we mayn't have backed you mayn't have backed they mayn't have backed
V-ing perfect
I mayn't have been backing you mayn't have been backing she mayn't have been backing we mayn't have been backing you mayn't have been backing they mayn't have been backing
Interrogative form
Simple form
may I back? may you back? may she back? may we back? may you back? may they back?
V-ing form
may I be backing? may you be backing? may she be backing? may we be backing? may you be backing? may they be backing?
Perfect
may I have backed? may you have backed? may she have backed? may we have backed? may you have backed? may they have backed?
V-ing perfect
may I have been backing? may you have been backing? may she have been backing? may we have been backing? may you have been backing? may they have been backing?
Interro-negative form
Simple form
mayn't I back? mayn't you back? mayn't she back? mayn't we back? mayn't you back? mayn't they back?
V-ing form
mayn't I be backing? mayn't you be backing? mayn't she be backing? mayn't we be backing? mayn't you be backing? mayn't they be backing?
Perfect
mayn't I have backed? mayn't you have backed? mayn't she have backed? mayn't we have backed? mayn't you have backed? mayn't they have backed?
V-ing perfect
mayn't I have been backing? mayn't you have been backing? mayn't she have been backing? mayn't we have been backing? mayn't you have been backing? mayn't they have been backing?