Detect API unavailability via HTTP 503, repeated 5xx, or timeout beyond the ASPSP's published SLA; log the failure timestamp and response code to establish a documented outage record
Check whether the NCA (National Competent Authority, e.g., FCA or BaFin) has granted the ASPSP an exemption from the fallback mechanism; if exempted, the ASPSP has no backup interface and you must surface a user-facing error
If no exemption applies, initiate the contingency fallback by navigating the user to the ASPSP's online banking interface; under PSD2 Article 33(6) / equivalent PSR provision, the ASPSP must allow screen-scraping-style access during certified API outages
Obtain prior NCA approval or EBA confirmation before activating the contingency mechanism in a non-outage situation; unauthorized use of the fallback outside a certified outage violates PSD2 Article 33
Record the start and end of every contingency access session; report prolonged API outages to the relevant NCA within the regulatory notification window specified by your home-state regulator
Re-test the primary dedicated API at regular intervals (e.g., every 5 minutes) and switch back as soon as it recovers; log the switchover for audit purposes
Known gotchas
The contingency/fallback mechanism does not apply to all ASPSPs; those that have received an NCA exemption from maintaining a fallback have no obligation to allow access via any channel during outages — your UX must handle this gracefully
Using the fallback when the dedicated API is functioning normally is prohibited under PSD2/PSR regardless of API performance degradation below your own SLA — the fallback threshold is ASPSP API unavailability, not your preferred response time
Some ASPSPs have changed their authentication flows since the fallback was designed; test the fallback path regularly as part of your operational runbook, not only during real outages
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