I must liaise you must liaise he must liaise we must liaise you must liaise they must liaise
V-ing form
I must be liaising you must be liaising he must be liaising we must be liaising you must be liaising they must be liaising
Perfect
I must have liaised you must have liaised he must have liaised we must have liaised you must have liaised they must have liaised
V-ing perfect
I must have been liaising you must have been liaising he must have been liaising we must have been liaising you must have been liaising they must have been liaising
Negation
Simple form
I mustn't liaise you mustn't liaise he mustn't liaise we mustn't liaise you mustn't liaise they mustn't liaise
V-ing form
I mustn't be liaising you mustn't be liaising he mustn't be liaising we mustn't be liaising you mustn't be liaising they mustn't be liaising
Perfect
I mustn't have liaised you mustn't have liaised he mustn't have liaised we mustn't have liaised you mustn't have liaised they mustn't have liaised
V-ing perfect
I mustn't have been liaising you mustn't have been liaising he mustn't have been liaising we mustn't have been liaising you mustn't have been liaising they mustn't have been liaising
Interrogative form
Simple form
must I liaise? must you liaise? must he liaise? must we liaise? must you liaise? must they liaise?
V-ing form
must I be liaising? must you be liaising? must he be liaising? must we be liaising? must you be liaising? must they be liaising?
Perfect
must I have liaised? must you have liaised? must he have liaised? must we have liaised? must you have liaised? must they have liaised?
V-ing perfect
must I have been liaising? must you have been liaising? must he have been liaising? must we have been liaising? must you have been liaising? must they have been liaising?
Interro-negative form
Simple form
mustn't I liaise? mustn't you liaise? mustn't he liaise? mustn't we liaise? mustn't you liaise? mustn't they liaise?
V-ing form
mustn't I be liaising? mustn't you be liaising? mustn't he be liaising? mustn't we be liaising? mustn't you be liaising? mustn't they be liaising?
Perfect
mustn't I have liaised? mustn't you have liaised? mustn't he have liaised? mustn't we have liaised? mustn't you have liaised? mustn't they have liaised?
V-ing perfect
mustn't I have been liaising? mustn't you have been liaising? mustn't he have been liaising? mustn't we have been liaising? mustn't you have been liaising? mustn't they have been liaising?