Sequencing front-to-back modernisation

Most IT budgets go to keeping old systems alive — published estimates put the share at 70–80% — and every regulatory change costs more to absorb on ageing platforms than on new ones. Doing nothing is not neutral; the liability grows every year.

The paper examines why the boldest response fails most often. McKinsey's research finds only about 30% of core platform transformations complete a full migration, 70% of digital transformations exceed their original budgets, and 7% cost more than double. The failure is structural, not managerial: a multi-year programme with one distant go-live accumulates risk out of sight while the legacy estate it was meant to retire keeps running, and keeps billing.

The full paper sets out the sequence that works: data and integration foundations first, then modernisation in slices tied to business value — a desk, an asset class, a process — with go-lives every one to two years and decommissioning in every wave, because the saving is only real when the legacy system switches off.