As AI advances, many digital services such as social media, job applications, medical diagnostics and policing are using algorithms to assess applicants, customers and citizens. OPACITY aims to remove prejudicial bias from AI by introducing a new tool for increasing the transparency of algorithms. Called the The OPACITY Trust Mark, this tool provides the first independent consumer instrument designed to hold the organisations that create Artificial Intelligence accountable for the effects of their creations. This trustmark is presented digitally and informs users when they are interacting with AI and how. In doing so, it allows anyone to query decisions made by AI and have them reviewed by humans.