  In this paper, we present a $q$-analogue of the polynomial reduction which
was originally developed for hypergeometric terms. Using the $q$-Gosper
representation, we describe the structure of rational functions that are
summable when multiplied with a given $q$-hypergeometric term. The structure
theorem enables us to generalize the $q$-polynomial reduction to the rational
case, which can be used in the automatic proof and discovery of $q$-identities.
As applications, several $q$-analogues of series for $\pi$ are presented.
