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Investment case12 min readUpdated 2026-09-18

How to Build a Business Case for AI in a Bank

A capital committee does not need to be told AI is transformational. It needs a denominator, a sensitivity table and an exit condition.

Written for CFO, capital committee sponsor, programme director

What you should take away

  • Scope the case to one queue with a measurable outcome, not to a capability.
  • Benefit is cost-to-serve avoided plus loss avoided, not FTE 'capacity released' unless the capacity is actually removed or redeployed.
  • Every material assumption carries an evidence type; the committee should see which ones are guesses.
  • Stage the capital release against measured resolution rate, not against delivery milestones.

The weakest AI papers in banking share a shape: a capability ('an AI agent for client service'), a benefit expressed as FTE equivalents, a single-point cost, and a nine-figure market statistic in the appendix. They get approved, and they get reopened.

The strongest ones look like credit papers. A defined exposure, a stated base case, named assumptions with sources, a sensitivity table, and conditions under which the facility is extended or withdrawn.

1. Scope to a queue, not a capability

"AI in client service" cannot be modelled. "Disputed card transactions under £100 in the retail contact centre" can: it has a volume, an average handling time, an owner, a quality measure, and a regulatory perimeter. Pick the queue where the outcome is already counted, because that is where the before-and-after comparison is defensible.

2. Establish today's economics first

InputWhere it comes fromEvidence type
Queue volumeContact centre reportingMeasured
Average handling timeWorkforce management systemMeasured
Fully loaded hourly costFinance, including supervision, premises, attritionMeasured
Repeat contact rateCRM linkage over a defined windowMeasured, often missing
Complaint and redress rateComplaints systemMeasured
Quality assurance sampling costOperations budgetMeasured

If three of these are unavailable, that is your first finding, and a cheaper piece of work than the AI programme.

3. Model the whole proposed workflow

The modelled cost is not the AI bill. It is the AI-attempted workflow cost, inference, retrieval, tools, platform and monitoring, escalation, retries, amortised implementation, plus the cost of everything the agent will not attempt, which stays exactly where it is.

Interactive model

Base case, staged by ambition

Set the share of the queue the agent attempts and the resolution rate you believe is achievable in year one. The model shows the before-and-after operating position.

Current annual human cost

£32.00m

AI-attempted workflow cost

£6.03m

Modelled annual operating difference

£16.37m

Total cost per successful outcome

£1.20

Share of queue attempted70%
Illustrative assumption
Autonomous resolution rate75%
Illustrative assumption
Implementation, amortised£500k/year
Illustrative assumption
Fully loaded agent cost£25.00/hour
Illustrative assumption

Where the cost sits

  • Human escalation£4.48m74%
    Calculated
  • Implementation, annualised£500k8%
    Calculated
  • Model inference£420k7%
    Calculated
  • Retrieval & data£180k3%
    Calculated
  • Failures & retries£180k3%
    Calculated
  • Platform, evaluation & monitoring£150k2%
    Calculated
  • Tools & APIs£120k2%
    Calculated

Largest modelled component: Human escalation (£4.48m). Outcome measured per successful autonomous resolution.

Illustrative defaults. A scenario output is not a forecast, and an operating difference is not a saving until the cost is actually removed from a budget.

4. Be honest about benefit realisation

  • Cost avoided is real only where headcount, overtime, outsourcer volume or premises actually reduce, with a named budget line and a date.
  • Capacity released is a benefit only if the released capacity is redeployed to work with a stated value.
  • Loss avoided (complaints, redress, fraud losses, breach exposure) is often the larger and better-evidenced benefit in regulated queues.
  • Revenue benefit from faster service should be modelled separately, with weaker confidence stated plainly.

5. Show the sensitivity, not just the answer

Which assumption should the committee interrogate?

Autonomous resolution rate ±5 pointsLargest effect
Escalated handling time ±2 minutesMaterial
Queue attempted ±10 pointsMaterial
Model price ±50%Minor

Relative shape under the illustrative defaults used across BillingEngine. Your ranking will differ, the point is to compute it rather than assume it.

6. Stage capital against measurement

  1. Tranche one funds instrumentation: resolution definition, repeat-contact measurement, eval set, baseline cost per resolution.
  2. Tranche two funds a limited live deployment on one queue, with the resolution-rate threshold written into the approval.
  3. Tranche three funds scale, and only after the measured rate holds for a defined period at production volume.
  4. Each tranche has a stated stop condition. An AI programme without one is not a business case; it is an aspiration with a budget code.

Apply this to your own workload

The figures above are illustrative assumptions. A BillingEngine assessment replaces them with your company's numbers and shows which assumptions decide the answer.