Two classes currently compete in the British GT Championship: GT3 and GT4. A consolidation of GT regulations and significant manufacturer support saw British GT first introduce the GT3 class in 2005. And from 2006 the category mirrored FIA Group GT3 and used near-identical regulations to the FIA GT3 European Championship.

GT3 rules include extensive Balance of Performance and handicap weights to make cars artificially more equal. Cost-saving measures saw the series’ previous premier class, GT2, phased out at the end of 2006.