In plain terms
Due diligence is the systematic examination of a counterparty before a binding commitment: an acquisition target's financials, contracts, technology and people; a vendor's delivery record and financial stability; a partner's regulatory exposure. Its output is a picture of what the buyer is actually acquiring or depending on, as opposed to what was presented.
Why sequencing decides its value
In most deals, diligence begins after the headline price and terms are broadly agreed. By then the acquirer has advisers engaged, a board expecting completion and executives publicly attached to the outcome. Findings are therefore absorbed as negotiation currency, a price chip here, a warranty there, rather than as evidence bearing on whether to proceed at all. The scope compounds the problem: it is set by the deal team, whose incentives point at closing, and it leans heavily towards what is auditable. Legal and financial exposure gets weeks of attention; whether the two operating cultures can run a single business gets a management presentation.
Where it goes wrong
Confirmatory diligence that starts from the conclusion and collects support for it. Red flags recorded in the report but never priced into the model, noted, caveated, and carried into completion unchanged. And the quiet narrowing of scope under time pressure, where the workstreams most likely to kill the deal are the ones that run out of time first.