According to the Department for Education (April 2012) a qualified teacher is one who has been awarded qualified teacher status (QTS) either by successfully completing a course of initial teacher training (ITT) or through other approved routes.
Teachers comprise the following:
a. Teachers with QTS or with the equivalent gained elsewhere in the European Economic Area (EEA);
b. Teachers without QTS, but with a professional qualification gained outside the EEA who have been in service for less than the 4 years (beyond which full QTS status gained in the UK is required);
c. Instructors without QTS, but with special qualifications in, or experience of, a particular subject. These can only be employed for only so long as a qualified teacher is unavailable.
An unqualified teacher is either a trainee working towards QTS; an overseas trained teacher who has not exceeded the four years they are allowed to teach without having QTS; or an instructor who has a particular skill who can be employed for so long as a qualified teacher is not available.