BBC iPlayer requires a licence from September 1st.

The loophole that has allowed many people to watch catchup TV without a television licence will be closed from 1st September when new legislation comes into force.

BBC iPlayer

Though many do have a licence and watch catchup as part of it, estimates predict it costs the BBC £150million per year for this.

The change applies to anyone watching BBC programmes on catchup or live, through any device or service such as Sky, Virgin or YouView. Oddly, the rules do not apply to other catch up services, only the BBC iPlayer.