The danger was in the gap between payments
A foreign-exchange deal is an exchange, but the two currencies usually travel through different banking systems. A bank might send one currency during its local business day, while the other side’s payment is scheduled for later, when the receiving country’s banks are open. Until both payments arrive, one party has performed and the other may still fail to pay.
That exposure is called settlement risk. In this case, the problem was amplified by the time difference: German banks had released marks, but the corresponding dollars were still due from New York. Once Herstatt could no longer make that later payment, its counterparties faced a choice between accepting a possible loss and stopping further deals until they understood who had been paid and who had not.
Why the shutdown reached beyond one bank
Foreign-exchange markets depend on banks trusting that the other side will deliver. A bank that has sent money cannot simply retrieve it if the matching payment does not arrive. And because many banks transact with one another, uncertainty about one participant can make them wary of settling with others, too. Freezing trading was a blunt way to limit the risk of sending more funds into an unsettled chain.
The episode gave this timing mismatch a lasting name: Herstatt risk, after the bank at the center of the failure. It also made clear that opening hours are not just a convenience in global finance; they can determine which side of a deal bears the danger if a bank fails mid-settlement.
Making the exchange arrive together
A key safeguard is payment-versus-payment settlement: the system releases one currency only if it can also release the other. That links the two legs of the exchange, so a bank is less likely to hand over its money and receive nothing in return. The practical lesson is simple: in a market that never really sleeps, payments need safeguards that do not depend on both countries’ business days lining up.
