The SIA stands for Security Industry Authority. Their role is to regulate the security industry within the private sector and ensure that work taking place is safe and individuals are qualified, safe and experienced enough to be doing what they are doing. Without a regulatory body like the SIA, the security industry as a whole would look very different.
The SIA have to issue individuals with licenses to make sure that the security industry is safe. This covers many different security professionals in its remit, including door guards, retail security guards, corporate security guards and people working privately in any other area of security.
They also have an approved contractor scheme. This is entirely voluntary but is designed to show consumers that an organisation has the seal of approval. The contractor would have to meet with a number of checks and regulations in order to gain approved contractor status in the first place.