The question is a bit unclear. But I'll have a go anyway. When a contractor says the did "abc for company xyz". You can always ring up xyz and ask for a confir

The question is a bit unclear. But I'll have a go anyway. When a contractor says the did "abc for company xyz". You can always ring up xyz and ask for a confirmation that the person did work for them and delivered abc to their satisfaction. When managing contractors, I give them clear specifications of what is required and what deliverables are expected and when. If they fail to deliver, then it's the end for them. Looking at another industry, e.g. home builders, you give the builder a set of drawings, specifications and that is what you manage their contract to. Many IT projects there's only a vague definition of what is required and the contractor is expected to somehow workout what the requirements are, design and then implement a solution. The only way that is possible is for the contractor to have a great deal of experience in the client's industry and typical requirements.