5 Ways Sponsors Can Challenge Costly ERP Estimates Without Getting Technical

If you’re sponsoring an ERP program, you’ve likely seen this moment.

A detailed estimate lands on the table.
The numbers look precise.
The rationale sounds confident.

And yet, something feels off.

Not because the team lacks experience — but because ERP estimates are often built on assumptions that stay implicit, optimism that goes untested, and risks that only surface months later.

Sponsors don’t need to become project managers or ERP experts to challenge this.
They need to know where estimates hide fragility.

This is the same dynamic that causes many ERP programs to drift even when everything looks “on track” — a pattern explored in FitGap’s analysis of ERP governance beyond theory:
👉 https://www.fitgapfinance.com/real-life-erp-implementation-lessons/

Challenging Estimates Is Not About Accuracy. It’s About Exposure.

ERP estimates are rarely “wrong” on day one.
They become wrong when reality diverges from what was assumed.

The sponsor’s role is not to re-estimate the project —
it’s to force assumptions, trade-offs, and ownership into the open.

These five challenges work at any stage and don’t require technical depth.

1. Make Assumptions and Exclusions Explicit — and Attach Consequences

What assumptions and exclusions does this estimate rely on, and which ones would immediately add cost if they prove false?

Why this matters:
Exclusions are the most common way estimates look affordable while risk is deferred.

What to listen for:

• Assumptions about data readiness, scope stability, user behavior
• Exclusions presented as “unlikely” but known to be unrealistic
• Clear articulation of what breaks first if an assumption fails

Red flag answers:

• “That shouldn’t happen”
• “We’ve never seen that before”
• “We’ll deal with it if it comes up”

This is especially common in areas like data migration, where risk is postponed until late phases — often with predictable consequences:
👉 https://www.fitgapfinance.com/data-migration-in-dynamics-365-how-to-avoid-the-most-costly-mistakes/

2. Surface the Success Conditions the Estimate Depends On

Which success conditions does this estimate assume, and how does the cost change if we fail to meet them?

Why this matters:
Many estimates are only valid under ideal conditions that are rarely sustained.

Typical success conditions quietly assumed:

• Fast, consistent decision-making
• High availability of internal resources
• Stable scope and priorities
• Clean data and disciplined users

What the sponsor should force:

• What happens to cost and timeline if these conditions degrade
• Which assumptions are most fragile
• Whether contingency exists — or optimism does

Red flag answers:

• “That’s the client’s responsibility”
• “We’ll manage it as we go”
• “The estimate assumes best effort”

When these conditions break down, governance — not execution — is usually the real failure point.

3. Separate What Is Truly Bespoke From What Should Be Accelerated

Which parts of this estimate are genuinely bespoke, and which are based on reuse, accelerators, or prior experience?

Why this matters:
High estimates often hide a “blank page” approach where reuse should exist.

What to listen for:

• Clear differentiation between standard and custom work
• Evidence of accelerators, templates, or proven patterns
• Justification for bespoke effort where claimed

Red flag answers:

• “Every client is different”
• “We prefer to design from scratch”
• Vague references to experience without concrete reuse

This confusion between “best practices” and real business needs is a recurring ERP trap:
👉 https://www.fitgapfinance.com/erp-best-practices-nuance-d365-finance/

4. Force a Minimum Viable ERP Conversation

What is the smallest version of this ERP that would still deliver real business value — and how much of this estimate is beyond that?

Why this matters:
Most ERP overruns come from building too much, too early.

What the sponsor should surface:

• What is essential for value creation
• What is additive but deferrable
• What is driven by comfort, not necessity

Red flag answers:

• “It’s all needed”
• “We can’t split it that way”
• “It’s better to do everything now”

Projects that skip this conversation usually pay for it later.

5. Assign Ownership to the First Likely Overrun

If this estimate is wrong, where will the overrun come from first — and who will own that decision when it happens?

Why this matters:
Estimates fail quietly until someone must take responsibility.

What the sponsor should force:

• Identification of the most likely overrun source
• Who decides when scope, cost, or timeline must move
• What happens when trade-offs are unavoidable

Red flag answers:

• “We’ll reassess later”
• “That depends on how the project goes”
• No clear owner for the decision

Unowned decisions are a consistent root cause of ERP failure — not tooling or effort.

Final Thought

ERP estimates don’t need to be perfect.
They need to be honest about where they’re fragile.

Sponsors don’t protect projects by accepting estimates at face value.
They protect them by challenging assumptions, forcing trade-offs, and assigning ownership early.

You don’t need to get technical to do that.
You need to make reality unavoidable.

This article is part of the FitGap Finance series — a business-first perspective on ERP governance, decision-making, and control beyond go-live.

🇫🇷 Version française: https://www.fitgapfinance.com/challenger-estimations-erp/