must untack
Regular verb: untack - untacked- untacked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must untack
you must untack
she must untack
we must untack
you must untack
they must untack 	I must be untacking
you must be untacking
she must be untacking
we must be untacking
you must be untacking
they must be untacking	I must have untacked
you must have untacked
she must have untacked
we must have untacked
you must have untacked
they must have untacked	I must have been untacking
you must have been untacking
she must have been untacking
we must have been untacking
you must have been untacking
they must have been untacking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't untack
you mustn't untack
she mustn't untack
we mustn't untack
you mustn't untack
they mustn't untack 	I mustn't be untacking
you mustn't be untacking
she mustn't be untacking
we mustn't be untacking
you mustn't be untacking
they mustn't be untacking	I mustn't have untacked
you mustn't have untacked
she mustn't have untacked
we mustn't have untacked
you mustn't have untacked
they mustn't have untacked	I mustn't have been untacking
you mustn't have been untacking
she mustn't have been untacking
we mustn't have been untacking
you mustn't have been untacking
they mustn't have been untacking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I untack?
must you untack?
must she untack?
must we untack?
must you untack?
must they untack? 	must I be untacking?
must you be untacking?
must she be untacking?
must we be untacking?
must you be untacking?
must they be untacking? 	must I have untacked?
must you have untacked?
must she have untacked?
must we have untacked?
must you have untacked?
must they have untacked? 	must I have been untacking?
must you have been untacking?
must she have been untacking?
must we have been untacking?
must you have been untacking?
must they have been untacking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I untack?
mustn't you untack?
mustn't she untack?
mustn't we untack?
mustn't you untack?
mustn't they untack? 	mustn't I be untacking?
mustn't you be untacking?
mustn't she be untacking?
mustn't we be untacking?
mustn't you be untacking?
mustn't they be untacking? 	mustn't I have untacked?
mustn't you have untacked?
mustn't she have untacked?
mustn't we have untacked?
mustn't you have untacked?
mustn't they have untacked? 	mustn't I have been untacking?
mustn't you have been untacking?
mustn't she have been untacking?
mustn't we have been untacking?
mustn't you have been untacking?
mustn't they have been untacking?