In several (colloquial) varieties of English around the world, the tag question is reduced to a single generalized invariant tag ‘isn't it?’. This is used irrespective of the general structure and semantic content of the matrix or main, superordinate clause that embeds it. Linguists started debating seriously on the actual use of tag questions in English since the early 1960s and 70s. The debates then were particularly focused on the use of tags on (elliptical) imperatives, with many concluding that the auxiliary in the imperative main clause is an elliptical will that serves as the source of input for the tag that is appended (Katz & Postal, 1964; Postal, 1966). Arbini (1969) discussed the putative parallel between tag imperatives and tag questions, and other early discussions on tags include Bolinger (1967), Huddleston (1970), and Klima (1964). The present discussion looks to a different direction. As already implied, it focuses on the emergence of isn't it? as a generalized invariant tag.