Deloitte · Technology / Operations · Intermediate · 25-35 min

Make vs. buy decision for enterprise ERP system

Make vs. buy decision for enterprise ERP system is an intermediate Deloitte technology / operations case interview that runs 25-35 min. Evaluate build vs. buy across total cost of ownership, implementation risk, and strategic fit. A strong answer works through 5 phases: Total cost of ownership; Implementation timeline and risk; Vendor selection criteria; Migration strategy; Training and change management.

Last updated 2026-09-05

The brief

A mid-cap manufacturing company’s ERP system is 15 years old and constraining growth. CFO is considering buying a modern SaaS ERP versus continuing to customize and maintain their legacy system. Compare the options and recommend.

How to approach it

  1. Total cost of ownership
  2. Implementation timeline and risk
  3. Vendor selection criteria
  4. Migration strategy
  5. Training and change management

What a strong answer does

  • Evaluate build vs. buy across total cost of ownership, implementation risk, and strategic fit.
  • Likely buy (SaaS) due to lower TCO, faster implementation, and reduced technical debt. Recommend comprehensive vendor selection process and phased migration to minimize operational disruption.

Practice drills

  • Build a 5-year TCO model for build vs. buy option.
  • Identify key vendor evaluation criteria for ERP selection.
  • Outline a phased migration plan to minimize downtime.
  • Assess skills gaps and training needs for new system.

Why this case

Tests financial modeling, vendor evaluation, and ability to balance multiple tradeoffs in a high-stakes decision.

Adapted from Deloitte Operations case (official sample).

Cases are written in each firm's style, written and reviewed by working consultants; they are not the firms' own published cases.

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