None. As the channel’s audience share is below the threshold at which broadcasters are obliged by Ofcom to offer subtitles, the subtitling service on BBC Parliament is a voluntary commitment of the BBC. It is the only parliamentary channel in the world to offer such a service.
The BBC announced in October of last year an increase in its subtitling of BBC Parliament from 450 hours per year to 810 hours, enabling more of the most important events to be offered in subtitling. The Government welcome this.