The SIA Approved Contractor Scheme (ACS) is a program designed to ensure that security services businesses meet certain quality standards and are considered trustworthy and reputable. Companies voluntarily apply to become approved contractors under this scheme and undergo assessments to determine their compliance with specified criteria. These criteria typically include factors such as professionalism, training standards, adherence to relevant laws and regulations, and ethical conduct. The scheme may involve criminality checks to verify the integrity of the individuals involved in the business. Once approved, contractors are recognised as meeting the required standards, which can enhance their credibility and reputation in the security industry.