What is netting, and why do banks not settle every payment?
Two banks owed each other billions today. At the end of the day, one of them moved a few million and the matter was closed.
Thousands of obligations. One transfer. The rest cancelled out.
Why gross settlement is impractical at scale
If every payment settled individually and immediately, every institution would need enough cash on hand to cover every outgoing payment at the moment it was made, without waiting for incoming ones.
The arithmetic does not work. The total value of payments flowing through a modern economy in a day is a large multiple of the cash actually available to settle them. Systems that do settle individually, like RTGS, are reserved for large-value payments precisely because that liquidity cost is worth paying only when the amounts are big enough that the alternative is dangerous.
Netting collapses the problem. Over a day, bank A owes bank B an enormous sum and bank B owes bank A a similarly enormous sum, and most of it cancels. What moves at the end is the difference, which is typically a small fraction of the gross. The liquidity saving is very large, and it is what makes high-volume retail payments economically possible at all.
What netting quietly creates
A window.
Between the moment an obligation arises and the moment it is settled, the obligation exists and the money has not moved. If a participant fails during that window, the others are exposed to what they were owed and had already acted upon.
This is settlement risk, and it is not theoretical. It is why payment systems layer protections on top of netting: collateral posted by participants, caps on net exposure, loss-sharing arrangements that spread a failure across survivors, and shortening the cycle so the window is smaller.
It is also the reason instant payment systems made a different choice. Settling in real time on a prefunded basis, as several newer national systems do, removes the window entirely at the cost of requiring participants to park money. Netting and prefunding are two answers to the same question, and each buys one thing by giving up the other.
Where you feel it as a customer
You do not, and that is the point. A retail payment appears instant because the messaging is instant. The settlement behind it happens on a cycle you never see, and the gap between the two is why a payment can look complete and still be reversed, and why a merchant receives money on a schedule rather than on each sale.
It is also why "the money is stuck" is so often a mismatch between two clocks rather than a fault. The instruction moved. The settlement had not yet come round.
Flatmates who buy each other coffees all month. Nobody transfers three pounds fourteen times. At the end of the month one person sends one payment and everyone is square. It works because they all expect to still be there at the end of the month, which is exactly the assumption the arrangement depends on.
Where you meet it
Every merchant settlement that arrives the next day rather than at the moment of sale. Every payment that looked instant and settled later. Every explanation of why large transfers cost more and clear differently from small ones.