ANSWER
How do you build a business case for legacy retirement?
Reviewed .
A business case for legacy retirement separates three boxes: the cost and risk of keeping the current operation, the temporary cost of transition and dual-run, and the operating cost after cutover. The decision becomes defensible only when every line has a source, owner and time window, non-financial benefits are explicit, and the no-cut scenario is also modeled.
Step by step
- Build a baseline for license, infrastructure, support, incidents, team hours and key-person concentration.
- Quantify risk from existing evidence without presenting uncertain probability as guaranteed savings.
- Separate setup, integration, dual-run, validation, security and rollback as transition costs.
- Model the post-cutover state, including recurring cost, exceptions and work that remains human.
- Define fit, minimum evidence, acceptable payback, approvers and no-cut criteria in advance.
How an agent does this
AgenticosCore keeps baseline, transition cost, new run cost and realized value as separate Value Ledger lines. A projection remains a hypothesis until dual-run, approved cutover and operational reconciliation.
Frequently asked questions
Can avoided risk count as savings?
Present risk separately with an owner and assumptions. Do not add probabilistic risk to cash savings as if it were realized revenue.
Which alternatives belong in the case?
At minimum: keep as-is, reduce scope, buy a market product and do not cut after dual-run. The case must allow a rational no-go.
Primary sources
- Guidance on the Legacy IT Risk Assessment Framework — UK Government
- Managing legacy technology — UK Government