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.

The SRO GT4 class was adopted in 2008 intended as a development class towards GT3. Regulations governing GT4 ensure the cars more closely resemble their road-going counterparts than GT3 machines, to control cost.