Monzo switched to Monzo Stand-in, a system it describes as its fully independent backup bank, shortly after midday on Wednesday, August 19, 2026, during an outage that left thousands of customers without normal access to its app. Card payments, cash withdrawals, and bank transfers kept working while the UK digital bank investigated, though some customers still reported declined cards.
“For a short period today, we activated Monzo Stand-in, our fully independent backup bank while we investigated an issue affecting customers,” Monzo said once service returned a few hours later. “This technical issue has been resolved, and all of our services are now back up and running.” The outage came a day after customers of Lloyds, Halifax, and Bank of Scotland were locked out of their accounts.
Two UK bank outages in two days
A backup bank of this kind is a parallel system, technically separate from the core platform, that can take over when the core stops responding. During the switchover, Monzo said essential services remained available. The list it gave customers shows exactly what such a system can do, and what it cannot:
- Card payments still go through.
- ATM cash withdrawals still work.
- Outgoing and incoming bank transfers are still processed.
- Customers can still freeze their card.
- Balances and the transaction feed, however, update with a delay, and some app features remain unavailable.
That asymmetry is the hallmark of degraded mode. The backup system can authorize and route payments, but without continuous access to the main ledger, it cannot show the exact state of an account in real time. Customers still reported card declines during the incident, a reminder that a switchover can succeed for the bank as a whole and still fail on individual transactions.
Payment continuity rests on three layers
No single safety net keeps payments running. Three mechanisms sit on top of one another, each covering a different kind of failure, and customers usually notice none of them.
| Level | Who takes over | What the customer can still do |
|---|---|---|
| Internal failover | A parallel system run by the bank itself | Pay, withdraw cash, and send transfers, with delayed updates |
| Card network stand-in | The network authorizes on the issuer’s behalf, under preset rules | Pay by card within set limits, with no access to the real balance |
| Full outage | No one | Use a payment method from another institution |
The second layer is invisible to customers and has been around for a long time. When an issuer stops responding to authorization requests, the card networks, Visa and Mastercard alike, apply stand-in processing: they answer on the issuer’s behalf, using parameters the issuer set in advance, including a maximum amount and eligible merchant categories. The issuer still bears the risk on any authorization approved during that window and receives the records afterward. That is why a bank outage does not immediately turn into cards declined at the point of sale.
UK rules make banks set a maximum tolerable outage
The UK has applied an operational resilience regime to banks, payment firms, and market infrastructures since March 2022. It rests on three linked obligations. Firms must identify the important business services whose disruption would harm customers or markets. They must set an impact tolerance for each one, meaning the maximum tolerable disruption. And they must map and test the technology chains that support those services. Since March 2025, firms in scope have had to be able to stay within those tolerances. A further set of rules, covering incident reporting and third-party providers, takes effect in March 2027.
The EU pursues the same goal by a different route
The EU’s Digital Operational Resilience Act (DORA), which has applied since January 2025, aims at the same outcome through a different method. It requires firms to classify major incidents and report them to supervisors, to run resilience testing, and to put critical IT providers under contractual oversight. The contrast is clear. The UK regime starts from the service delivered to the customer and how long it can acceptably be down. The EU regime starts from the risk management framework and the outsourcing chain.
Two bank outages in two days in the same market also show what a digital-only bank has at stake. A branch network offers a fallback that is degraded but real. An app that stops responding offers none, unless the bank has built, tested, and paid for a second technical bank whose only purpose is never to be used.