Wiktionary
n. (context legal English) A legally binding process during which a potential buyer evaluates the assets and liabilities of a company.
Wikipedia
Due diligence is an investigation of a business or person prior to signing a contract, or an act with a certain standard of care.
It can be a legal obligation, but the term will more commonly apply to voluntary investigations. A common example of due diligence in various industries is the process through which a potential acquirer evaluates a target company or its assets for an acquisition. 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.
Usage examples of "due diligence".
Now I remember some angry mail from the Dentist's due diligence harpies because the survey was costing too much and taking too long.
She had most likely procured the due diligence report from the archives warehouse on a Freedom of Information petition.
Back in January, when he received the disappointing report from Nolly Wulfstan, Junior was not convinced that the private detective had exercised due diligence in his investigation.
Judging by how I felt about my own sisters' husbands, if he loathed Mandumerus he would look after me with due diligence.