Operational Readiness Check Before Each Migration Wave

Check Integration Readiness Before Each Wave

TSB's 2018 migration drew 225,492 complaints. An operational readiness check before each wave turns go or no-go into a decision on evidence.

Alexander Kiel

Business Analyst · Banking & Wealth Management

07.02.2026 · 7 MIN READ · BUSINESS INTEGRATION

ON THIS PAGE

1. Set Exit Criteria for Every Wave

2. Test With Real Volumes

3. Confirm Third-Party Readiness

4. Prepare the Business Teams

5. Run the Operational Readiness Check

6. Plan the Fallback and Hypercare

Sample case: TSB

In short

FAQ

Change is a leading cause of serious IT incidents in banking. UK retail banks reported 446 major operational incidents to the FCA in 2025. Change management was the most frequent driver at 24.2%. An operational readiness check before each migration wave is how a bank keeps that risk under control.

Big changes carry most of it. In its review of technology change, the FCA found that 24% of high-severity incidents had a root cause relating to change. A bank integration bundles many such changes into a few cut-over weekends.

Integrations move in waves. Every wave is a decision. A readiness check turns that decision into evidence. Would your steering committee know today what has to be true before the next wave goes live?

A readiness gate before a migration wave: evidence on data and testing, third parties, business teams and fallback feeds one integration readiness check, which leads to go, go with conditions or no-go

STEP 1

Set Exit Criteria for Every Wave

Agree in numbers what ready means for each migration wave before it is planned in detail. Each criterion needs a threshold, an evidence source and one owner: reconciliation breaks within tolerance, no open critical defects, trained staff above an agreed share. Criteria written in the week of cut-over tend to bend to fit the plan.

The FCA found that major changes were twice as likely to result in an incident as standard changes. Firms with change governance in place for over a year experienced a lower proportion of incidents.

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Write measurable go criteria before detailed wave planning

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Name one owner and one evidence source per criterion

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Freeze the criteria once the steering committee approves them

Could your team say today which numbers would stop the next wave?

Keep in mind: Readiness criteria are not a test plan. They summarise test results, business readiness and open risks for a decision-maker.

STEP 2

Test With Real Volumes

A migration wave can pass every functional test and still fail on its first Monday. Rehearse with production-sized data, peak transaction volumes and the real interfaces. Reconcile every account and position after each rehearsal. Time the full run against the cut-over window.

The FCA found that firms are still heavily reliant on manual testing and peer review, both prone to human error. Load matters as much as accuracy: on the first working day after its 2018 migration, about 10% of roughly 900,000 internet banking logins at TSB succeeded.

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Run at least one full rehearsal with production-sized data

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Reconcile accounts, positions and balances after every rehearsal

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Test peak volumes, not only an average day

When did your team last rehearse a cut-over with a full copy of production data?

Keep in mind: A rehearsal that finished on time only because steps were skipped is a failed rehearsal. Record what was cut.

STEP 3

Confirm Third-Party Readiness

Most bank integrations depend on software vendors, outsourcers and the target bank's IT provider. Ask each one for evidence of readiness, not a letter of intent: completed tests, staffed support for the cut-over weekend and named contacts with authority to act.

The FCA found that over 20% of incidents at third parties were caused by change and that most firms did not effectively track third-party changes. A supplier that changes its own systems in the weeks before your wave adds risk you cannot see.

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List every third party touched by the wave

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Ask for test evidence, not assurance letters

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Agree support hours and escalation for the cut-over weekend

Which supplier could stop your next wave and when did you last check its readiness?

Keep in mind: A supplier's confirmation is only as good as its own suppliers. Ask who they depend on for the same weekend.

STEP 4

Prepare the Business Teams

IT readiness is only half of an operational readiness check. Relationship managers, operations staff and the call centre need training, updated procedures and answers to the questions clients will ask in the first week. I have worked on both sides of integrations with a leading Swiss bank, having been part of the acquired business in 2017–18 and the acquiring organisation in 2026.

Client demand after a migration wave is easy to underestimate. After its 2023 Postbank migration, Deutsche Bank said it saw unexpected levels of client enquiries which led to backlogs. BaFin then appointed a special representative to monitor the bank. My article on transferring clients between banks covers the client letters that reduce this volume.

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Train staff on the target processes before each wave

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Staff the call centre for peak volumes in the first week

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Give branches a short guide to the most frequent questions

How many extra calls can your service centre handle in the week after a wave?

Keep in mind: Business readiness needs its own sign-off. An IT go does not mean the branches are ready.

STEP 5

Run the Operational Readiness Check

Bring the readiness evidence to one steering committee meeting a few days before cut-over. The PMO shows each criterion as met, not met or met with a risk the business accepts. The steering committee then decides go, no-go or go with conditions. The decision is recorded with the names of those who took it.

A formal board is no guarantee of scrutiny. The FCA found that change advisory boards approved over 90% of the major changes they reviewed. My article on the one-page decision paper shows how to present a go or no-go so that the committee sees the risks, not only the progress.

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Hold the readiness check early enough to act on a no-go

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Show each criterion as met, not met or accepted risk

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Record the decision, the conditions and the decision-makers

Has your steering committee ever said no-go and what would it take today?

Keep in mind: A no-go is a result, not a failure. Fix the date of the next possible wave before the readiness check.

STEP 6

Plan the Fallback and Hypercare

Every migration wave needs a point of no return, a tested fallback before it and a hypercare plan after it. Agree who can call a rollback, by what time and on which signals. After cut-over, review incidents, reconciliation breaks and client contacts daily until they are back to normal.

The PRA expects banks to test regularly their ability to remain within impact tolerances in severe but plausible scenarios. A failed migration wave is one of them. TSB's own review shows how fast it escalates: in 2018, enquiries exceeded the contingency resources already in place.

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Define the point of no return for each wave

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Rehearse the rollback, not only the cut-over

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Hold daily hypercare reviews until incidents are back to normal

Who in your bank can stop a cut-over at 2 a.m. and do they know it?

Keep in mind: Hypercare ends on agreed criteria, not on a date. Keep the extra support until the numbers say otherwise.

How Do We Heal Medicine? | Atul Gawande (Surgeon and Writer @ TED)

SAMPLE CASE

TSB

In July 2015, Sabadell acquired TSB, which still ran on the Lloyds Banking Group platform. TSB engaged Sabadell's IT subsidiary SABIS to build a new platform and migrate to it. The migration took place over the weekend of 20 to 22 April 2018, for a bank with 5.2 million customers.

The FCA found that testing only concluded the day before the decision to migrate was taken. It also found that supplier confirmations were partly statements of good intention. The PRA later fined the former CIO for assuring the board of the supplier's readiness while TSB had not itself obtained sufficient assurance.

TSB returned to business as usual only in December 2018. It received 225,492 complaints, paid £32.7 million in redress and was fined £48.65 million by the FCA and PRA in December 2022.

Key takeaway: A go decision is only as strong as its evidence. Finish testing well before the readiness check, verify supplier readiness yourself and show the steering committee what is still open.

"The failings in this case were widespread and serious which had a real impact on the day-to-day lives of a significant proportion of TSB's customers, including those who were vulnerable."

Mark Steward (Executive Director of Enforcement and Market Oversight @ FCA)

In Short

An operational readiness check turns each migration wave into a decision based on evidence. Set the criteria early, test with real volumes, confirm third parties, prepare the business teams, decide in one meeting and plan the fallback.

The result is a wave that goes live when it is ready, or a no-go taken early enough to protect clients, staff and the integration timeline. Start with the criteria for your next wave.

Frequently Asked Questions

What is an operational readiness check before a migration wave?

An operational readiness check is a formal review held a few days before each migration wave. The PMO presents evidence against agreed criteria: test results, reconciliation, supplier confirmations, business readiness and fallback plans. The steering committee then decides go, no-go or go with conditions. The decision, its conditions and the people who took it are recorded for audit.

What are typical go/no-go criteria for a migration wave?

Typical criteria cover data, technology, people and risk. Examples are reconciliation breaks within tolerance, no open critical defects, rehearsals completed within the cut-over window, signed confirmations from key suppliers, trained staff in branches and operations and a tested rollback. Each criterion needs a measurable threshold, an evidence source and one owner. The steering committee approves the criteria before wave planning starts.

Who decides go or no-go before a migration wave?

Usually the integration steering committee, based on the readiness check prepared by the PMO. Business owners confirm that their teams are ready, IT confirms the technical criteria and risk functions raise any concerns. The committee should meet early enough to act on a no-go and agree in advance who can call a rollback during the weekend. The decision is then minuted.