Default is the legal state a debtor enters once performance is overdue and the requirements of the law are met. It matters because most remedies for non-performance, in particular damages for delay and rescission, only become available once the debtor is in default.
Legal basis
Articles 6:81 to 6:83 of the Dutch Civil Code govern default. The main route is Article 6:82: the creditor sends a written notice of default giving a reasonable period for performance, and default arises once that period passes without performance.
Article 6:83 lists the cases where default arises without any notice. The most important are a fixed deadline that has passed, an obligation to pay damages arising from tort, and a communication from the debtor from which the creditor must conclude that performance will not follow.
Why it is the pivot of most disputes
Non-performance and default are two different things. A supplier who delivers late has failed to perform, but until default arises the buyer cannot claim damages for the delay or rescind. Conversely, once performance has become permanently impossible, default is not required at all: the remedies are available immediately.
Default also shifts risk. From the moment it arises, the debtor bears the risk of loss or damage to the object of the obligation, and statutory interest starts to run.
Where it goes wrong
The recurring error is treating a delivery date in a contract as automatically fatal. It usually is not: whether a date is a fixed deadline within the meaning of Article 6:83 depends on the wording and the context, and a date agreed as an estimate does not qualify. Where there is doubt, sending a notice of default costs nothing and removes the question.
Related terms
See also notice of default, breach of contract and rescission of a contract.
Our civil law team advises on contractual disputes and the steps that precede a claim.

