People who only watch BBC shows on catchup will be legally required to have a TV licence from 1 September, when new legislation to close the so-called “iPlayer loophole” comes into force.

Though the vast majority of households own a TV licence, those without one who only watch catch-up content and not live broadcasts were technically exempt from paying the £145 a year charge.

The government had promised to close the loophole, which already costs the BBC about £150m a year and is likely to increase, during negotiations last summer that also saw the corporation agree to shoulder the £750m burden of free licence fees for the over-75s.

The changes apply to anyone watching BBC programmes on catchup through any device and third-party services such as Sky, Virgin or BT.

However, while a TV licence is currently required to watch live broadcasts from other terrestrial providers such as ITV and Channel 4, the new rules do not apply to non-BBC on-demand services such as ITV Hub or Channel 4’s All4.

BBC radio content listened to on-demand on iPlayer is also not covered by the legislation, as is content from Welsh broadcaster S4C.

A spokesperson for TV licensing said: “As of 1 September 2016, a change in the law means you need to be covered by a TV licence to download or watch BBC programmes on demand – including catchup TV – on BBC iPlayer. This applies to all devices. The change will not affect the huge majority of households which are already licensed.

“Fewer than 2% of households only watch catchup – and only those watching BBC iPlayer as part of their catchup and on-demand viewing will need to buy a licence from September. You will not need a TV licence to download or watch programmes on demand from other providers, such as YouTube, Netflix, ITV Hub, All 4 or Demand 5. All unlicensed households are being mailed and a publicity campaign will happen before 1 September.”