Rollout phasing / April 2026
ITIL rollout phases and where budgets overrun
A three-phase rollout (foundation, embed, optimise) typically runs 12 to 24 months in enterprises over 100 IT staff. Phase costs are uneven, and the overruns are predictable.
Section 01
Phase 1: Foundation
Months 1 to 6. Training cohort scheduled, internal champion identified, baseline service catalogue documented, change advisory board chartered. Visible deliverables: certified staff and process documentation. Typical phase cost 30 to 45% of year-one programme spend.
Where it overruns:
- Training cohort scope creep. Initial estimate of "100 staff to certify" expands to 130 once shared-services functions are included. Per-head cost remains; programme cost rises 30%.
- Missing internal champion. Where leadership has not allocated a named ITSM lead with at least 0.4 FTE protected, the programme stalls in months four to six. Remediation cost is consultancy backfill at premium rates.
Section 02
Phase 2: Embed
Months 7 to 14. Processes operationalised across teams, tooling aligned to the documented design, change management replacing ad-hoc approval. Typical phase cost 35 to 50% of year-one spend.
Where it overruns:
- Process tooling alignment underestimated. The existing ITSM platform supports the process on paper but enforces a different workflow in practice. Reconfiguration cost £12k to £55k typically.
- Change management cost missing from the business case. Training certifies people; embedding requires behavioural change, which requires communications, line manager support, and forum time. Typically £15k to £45k of programme time not accounted for at kickoff.
Section 03
Phase 3: Optimise
Months 15 to 24. Process tuning based on operational data, metrics rolled up to leadership, recertification cycle initiated for the earliest cohort. Typical phase cost 15 to 25% of year-one spend, plus ongoing surveillance from year three.
Where it overruns:
- Recertification cycle not modelled. From year three the cohort certified in year one needs CPD credits or re-examination. Annual ongoing cost 8 to 14% of year-one training spend.
- Multi-entity scope expansion discovered late. An acquired subsidiary or international division is brought in scope after the programme is supposedly complete. Each new entity adds programme management overhead disproportionate to its training population.
Section 04
Five most common overrun causes
Predictable cost overruns by phase
| Cause | Typical phase | Cost impact |
|---|---|---|
| Time off tools underestimated by half | Phase 1 | +£30k to +£90k |
| Internal champion under-resourced | Phases 1 and 2 | +£45k to +£140k consultancy backfill |
| Tool platform change forced mid-rollout | Phase 2 | +£180k to +£800k+ |
| Multi-entity scope discovered mid-programme | Phase 2 and 3 | +25 to 45% per entity |
| Recertification cycle not budgeted from year 3 | Year 3+ | +8 to 14% of yr 1 annually |