Negative Polarity: Finite vs Adjunct; Mood vs Residue

 Halliday & Matthiessen (2014: 145):

you may not leave before the end (‘are not allowed to’): not is part of Finite

you may not stay right to the end (‘are allowed not to’): not is part of Residue

Halliday & Matthiessen (2014: 177):

Halliday & Matthiessen (2014: 176n):

The principle is rather complex, but it works as follows: if the agnate finite clause is negative (as shown by the tag; e.g. she was never given a proper chance, was she?) then the negative Adjunct functions as Mood element. If the agnate finite clause is positive (e.g. she could not have known about it, couldn’t she?) then the negative Adjunct forms part of the Residue.