There is no reliable universal number of days or weeks for changing an API supplier. The schedule depends on how much of your service relies on the API, the migration and testing work, your contract, and any rules that apply to your organization. A supplier change does not automatically require regulatory approval: depending on the jurisdiction and the arrangement, the obligation may instead be to report the change—or there may be no specific regulator filing.
Why there is no standard supplier-switch timeline
Replacing an API supplier is a migration, not simply a matter of changing an endpoint in an application. The new service may differ in its data model, authentication, permissions, limits, error responses, availability commitments, or behavior when a request fails. Each difference can affect software, users, downstream systems, and operational procedures.
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The available official guidance does not establish an industry-wide average duration for replacing a commercial API supplier. It also does not provide a universal approval checklist, migration-cost estimate, or supplier ranking. Giving a single estimate such as “two weeks” or “three months” would therefore imply certainty the evidence does not support.
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Build a schedule from the work that must be done
Use these phases to produce a project estimate. Assign an owner and estimate for each phase only after the relevant systems, contract terms, and regulatory scope are known. Some phases can overlap; others depend on earlier decisions. For example, implementation can start before all test cases are complete, but a safe cutover depends on the new integration passing the tests that matter to your service.
1. Define the service boundary
List the functions the current API performs and identify every application, team, customer journey, or external partner that consumes them. Record which endpoints and data are in use—not just which ones the original integration was built to support. Include scheduled jobs, reporting, monitoring, and any less-visible process that relies on the supplier.
At this stage, clarify what “supplier” means in your case: a commercial API provider, an open-banking interface, or a provider of infrastructure that supports a regulated service. That distinction affects both the migration and the compliance questions. An API used only for a non-regulated internal task should not automatically be treated like a provider whose failure would interrupt a regulated activity.
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Review the current contract before committing to a cutover date. Look for termination notice, renewal dates, transition assistance, data export and deletion, service continuity during exit, and restrictions or dependencies involving subcontractors. Contractual notice can determine when you may leave; it does not tell you how long the replacement integration will take to build.
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Establish how the service will continue if the new integration is delayed or the old supplier is unavailable during the transition. Agree who can authorize an extension, what support the incumbent must provide, and how data will be returned or deleted at the end. These are practical exit-planning questions, not a substitute for checking the specific legal and regulatory requirements that apply.
3. Map and implement the differences
Compare the suppliers at the level of actual integration behavior. Inventory data fields and formats, authentication and consent flows, rate limits, error handling, service levels, incident procedures, and the functionality your users depend on. A replacement that covers the same headline feature may still require substantial changes if its details differ.
Build an impact list that connects each difference to the code, configuration, operational process, or customer communication it affects. This makes the estimate more useful than counting endpoints alone: one endpoint with a different consent model can affect more of the service than several endpoints with compatible behavior.
4. Test the complete service path
Test more than whether a successful request returns a response. Check expected data, permissions, failures, timeouts, rate-limit behavior, recovery, and the effect on the applications that consume the API. Include operational checks such as alerting and incident handling, and verify that the migration has not created gaps in audit or reporting records where those are relevant to your service.
The Saudi Central Bank’s open-banking materials describe a framework and lab for development, testing, and certification. This is a jurisdiction-specific example of a testing environment; it should not be presented as a universal requirement for API migrations. Likewise, UK Open Banking guidance calls for testing in the context of standards transitions, not for every commercial supplier change.
5. Plan cutover, observation, and retirement
Choose a cutover method appropriate to the integration. If feasible and permitted, run both services temporarily, compare results, and move traffic or users in controlled stages. Define in advance what success looks like, what signals would pause the rollout, who can initiate rollback, and how a rollback will work without losing or duplicating data.
Monitor the replacement after the switch for errors, latency or availability issues, unexpected data differences, and customer or operational impact. Keep the old service available for the agreed transition period where the contract and technical design permit. Retire it only after the replacement is stable, dependent consumers have moved, and required data handling and access removal are complete.
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What the UK Open Banking transition periods do—and do not—mean
Open Banking Limited’s version guidance, latest version published 18 March 2026, gives concrete time periods for transitions between Open Banking Standard versions. These periods are useful when that specific standards-change guidance applies. They are not a general schedule for replacing one commercial API supplier with another.
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| Open Banking standards-change guidance | Stated period | How to interpret it |
|---|---|---|
| Notice to third-party providers before an update is required, except in an emergency | At least three months | A notice period for the standards transition described by Open Banking Limited, not a universal supplier-termination notice. |
| Implement a new major standard version | Within six months | A version implementation window under that guidance, not an estimate for all work involved in changing suppliers. |
| Implement a new minor standard version | Within three months | A separate version implementation window under the same guidance. |
| Recommended dual running for a major version | At least six months | A recommendation for running versions in parallel during the specified standards transition. |
| Recommended dual running for a minor version | At least three months | A recommendation for that minor-version transition, not a general requirement for every API migration. |
These figures describe different things: notice, implementation, and recommended parallel operation. Do not add them together as though they formed a single mandatory supplier-switch duration, or apply them automatically outside the relevant UK Open Banking standards context. The applicable contract, technical scope, and other regulatory obligations still need their own assessment.
How to determine whether a regulator must be told or asked
First identify the jurisdiction, regulated entity, license or authorization, service, and supplier role. Then determine whether the arrangement falls within a specific reporting, approval, or licensing rule. There is no evidence here for a universal rule that every API supplier replacement needs prior approval.
- Identify the regulated activity and entity. Confirm which organization uses the API, what regulated service it supports, and which regulator and authorization apply.
- Characterize the arrangement. Establish whether the provider is a third party, an outsourcing provider, a material or critical provider under relevant rules, or a supplier with another status. A software label alone does not determine regulatory treatment.
- Assess the change. Ask whether the change creates a new arrangement, significantly changes an existing one, affects a license option, or changes the regulated activity. Do not assume that changing software has the same effect as changing a licensed service.
- Check the exact rule and timing. Establish whether the obligation is advance approval, notification, reporting, recordkeeping, or none of those. Confirm the deadline and any transitional provisions with the regulator’s current rules and qualified compliance or legal advisers.
- Document the decision. Keep the reasoning, scope, risk assessment, approvals, filings, and implementation plan together so the organization can demonstrate how it reached its conclusion.
UK FCA: reporting material third-party arrangements from 18 March 2027
The FCA states that, from 18 March 2027, firms within the scope of its new requirements must tell it when entering a material third-party arrangement or significantly changing an existing one, and must maintain an annual register of material arrangements. The FCA describes this as reporting; it should not be described as prior approval. A firm must establish whether it and the specific change are in scope before treating the requirement as applicable.
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UAE: a license-option rule is not a general API replacement rule
The Central Bank of the UAE’s Open Finance Regulation says that a licensee seeking to change options selected under its license must re-apply and obtain Central Bank approval. That is a specific rule about changing selected license options. It is not evidence that every UAE API supplier replacement requires approval, and it should not be generalized beyond the rule’s context.
Do not confuse two meanings of “API” in FCA materials
In this article, API means application programming interface. On an FCA page about payment-institution applicants, “API” means “authorised payment institution.” That page describes authorization conditions for becoming an authorised payment institution; it does not state that changing a software API supplier requires re-authorization. Check the page’s context before relying on the abbreviation.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Compare the replacement on migration risk, not just features
A supplier comparison should reveal the work and risk of the switch, not only whether both products appear to do the same job. Score each item against your service’s actual needs, and record any requirement that cannot be verified before signing or beginning the migration.
| Comparison area | Questions to answer |
|---|---|
| Functional coverage | Does the replacement support every function, endpoint, and data use that current consumers need? |
| Compatibility and migration effort | How do formats, authentication, permissions, errors, limits, and versioning differ, and what code or process changes follow? |
| Data portability and exit support | Can the organization export required data, obtain transition assistance, and complete return or deletion obligations? |
| Security and authentication | How are identities, credentials, permissions, consent, and access managed through normal operation and cutover? |
| Availability and incidents | What service commitments, incident communications, and recovery arrangements are documented? |
| Regulatory and audit support | Can the provider support the organization’s relevant audit, evidence, and compliance needs? |
| Total cost and contract terms | What are the full service and transition costs, termination terms, renewal dates, and continuity obligations? |
| Testing and parallel operation | Can both services be exercised safely during transition, and is there a suitable test environment? |
The available official material does not rank providers or quantify typical switching costs. Treat those as questions for a supplier evaluation and contract review, not as values that can be inferred from standards guidance.
Common planning errors to avoid
- Using a version deadline as a supplier-switch estimate. Open Banking’s stated windows concern specific standards-version changes; a supplier replacement can involve different dependencies and obligations.
- Calling a reporting obligation “approval.” The FCA’s 2027 material-third-party requirement is described as reporting. Approval and reporting are not interchangeable.
- Assuming a software change is automatically immaterial—or material. Determine the status of the arrangement under the relevant rules instead of deciding from the word “API.”
- Starting from the visible endpoint alone. Undocumented consumers, scheduled work, or operational procedures can extend the scope; inventory actual use before estimating.
- Leaving exit planning until cutover. Termination notice, data return, transition support, and continuity are contractual questions that can constrain the schedule from the outset.
- Cutting over without a rollback condition. Decide what failure signals stop the rollout and how the service can return to the prior path before traffic moves.
What to put in a credible estimate
A useful estimate is a range tied to explicit assumptions, not a number presented as an industry norm. State which consumers are in scope, what the supplier comparison has confirmed, whether contract notice constrains the date, what testing and parallel-running approach is feasible, and what regulatory determination remains open. Separate engineering completion from the earliest permitted termination date and any required notice or report.
For a regulated organization, make the compliance decision a tracked dependency with a named owner. If scope or materiality is unclear, do not quietly assume that no filing is required; establish the answer under the applicable rules before setting a definitive cutover. For a non-regulated integration, regulatory approval may not be relevant, but security, privacy, contractual, and continuity requirements can still shape the migration.
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