What does it typically cost a large retail company (~$15B turnover pa) to implement an ERP solution (& ongoing run estimates)?

For a large retail enterprise with ~$15B in annual revenue, the total cost of implementing an ERP solution—including software, implementation, and support—can be substantial. Below is a typical high-level cost breakdown based on a vendor-led approach:
 • Software Subscription (5 years): ~$1M annually, totaling $5M over five years.
 • Implementation (One-Time, 12 Months): ~$15M, covering system configuration, integrations, data migration, change management, and program governance.
 • Post-Go-Live Support (5 years): ~$1M per year for a vendor-managed support model, totaling $5M.

This brings the total cost estimate to ~$25M over a five-year period.

In parallel, it’s recommended to outsource accounting managed services to free up internal capacity and focus enterprise teams on program delivery and strategic oversight.

Additionally, you’ll need to account for internal staffing to sustain and evolve the ERP ecosystem. A typical setup includes ~15 full-time headcount across IT, finance systems, and business operations to ensure long-term success.

That can vary from ERP solution to another also if there is a migration process or new implementation.

Based on the company fiscal taxes, accounting and finance model complexity it must be calculated, is not the same implement a ERP solution in one country rather than implement in multiple countries with many currencies and taxes and intercompany processes.

I know about a multicompany implementation that is near to 20MM but it has the complexity of many countries, many integrations in the supply chain and local taxes rules and the project will last around 5 years.

This is an open wide question that need a fine tuning in many aspects like people involved, ERP solution chosen, partner chosen and model of implementation, if one shot or by core processes and next processes.

I have not done it yet, but I have been looking into it. It is a multi-year project, and it will require a transformation committee/office to oversee the implementation/transition.