Due diligence is the investigation or exercise of care that a reasonable business or person is expected to take before entering into an agreement or contract with another party, or an act with a certain standard of care.

The theory behind due diligence holds that performing this type of investigation contributes significantly to informed decision making by enhancing the amount and quality of information available to decision makers and by ensuring that this information is systematically used to deliberate in a reflexive manner on the decision at hand and all its costs, benefits, and risks.

The investors examine the financial statements and books and records of the company, and all aspects of its operations. They may require that certain matters be corrected before agreeing to the transaction, e.g. new employment contracts or stock vesting schedules for key executives. At the end of the process the company offers representations and warranties to the investors concerning the accuracy and sufficiency of the company's disclosures, as well as the existence of certain conditions (subject to enumerated exceptions), as part of the stock purchase agreement.