Due diligence is a comprehensive evaluation of a person or business before entering into a formal relationship. It combines multiple checks — identity, legal, financial, regulatory, and reputational. For businesses, it includes validating legal registrations, licenses, directors, and market reputation. For individuals, it includes employment, criminal, and financial reviews. This ensures trust and reduces exposure to fraud, litigation, or compliance breaches, especially in mergers, partnerships, or high-risk hires.