When trying to access BBC iPlayer, you might get a notification informing you that a UK TV license is required to watch any program on the site. When prompted, many sources report you can simply click "I have a TV license".
BBC apparently depends on the honor system to keep viewers honest and does not require actual proof that the user has a TV license. This message was added to iPlayer's terms of service in September 2016.
Access to the BBC iPlayer streaming service now requires viewers to register a BBC account and input a valid UK postcode. The form does not seem to verify whether or not the registrant actually lives within the postal code they input, so as long as you have a UK IP address, you should be okay.