# The Spreadsheet Trap

Spreadsheets are the right tool to start IBP. The trap is not knowing when to stop.

# The Pattern

An organization launches IBP using Excel — and it works. A demand planning analyst builds a forecast model, creates a supply-demand balancing sheet, and puts together a monthly review deck. The process runs for 6-12 months, gains traction, and starts expanding to more product families, more regions, more participants.

Then the cracks appear. The "master spreadsheet" has grown to 50+ tabs and takes 10 minutes to open. Version control is a filename convention (IBP_Plan_v7_FINAL_v2_RD_edits.xlsx). Three people maintain copies with different updates. The demand plan lives on someone's OneDrive and nobody else can find it. Preparing for the monthly IBP meeting takes the analyst 3-4 days of manual data gathering, reconciliation, and formatting — leaving almost no time for actual analysis.

The organization knows it needs to change but feels stuck: the spreadsheets contain institutional knowledge that's hard to migrate, the analyst who built them is the only person who understands them, and the cost of a planning tool feels hard to justify when "Excel works."

# Why It's Tempting

Fast and free. No procurement cycle, no IT project, no vendor selection. You can build a working IBP model in a week.
Everyone knows Excel. No training needed. Users can see and modify the logic. Transparency is high.
It genuinely works at small scale. For 3-5 product families at one site, a well-built spreadsheet is perfectly adequate. The advice to "start simple" legitimately points here.
Low commitment. If IBP doesn't work out, you haven't invested in software you need to justify. Spreadsheets are a low-risk starting point.

All of this is true. The anti-pattern isn't starting with spreadsheets — it's staying with them past the point where they scale.

# Why It Fails (Eventually)

# Version chaos

Multiple people editing copies of the same file creates divergent versions of the plan. Nobody knows which version is current. The monthly reconciliation meeting starts with 20 minutes of "which numbers are we looking at?"

# Manual errors erode trust

Complex spreadsheets accumulate formula errors, broken links, and incorrect references. A misplaced row, a pasted-values overwrite, or a broken VLOOKUP can silently corrupt the plan. When errors are discovered — usually in front of leadership — trust in the process drops.

# Scenario modeling becomes impractical

Scenario planning requires running multiple demand-supply-financial projections side by side. In a spreadsheet, this means duplicating tabs, manually adjusting inputs, and hoping the formulas still work. Most organizations give up on scenarios rather than maintaining parallel spreadsheet versions.

# Single point of failure

The analyst who built the spreadsheets becomes indispensable. They can't take vacation during IBP week. If they leave, the process collapses because nobody else understands the model. This is a people risk masquerading as a technology problem.

# Prep time exceeds meeting time

When 3-4 days of manual work produces a 90-minute meeting, the ratio is broken. The analyst has no time for value-added analysis because they're spending all their effort on data plumbing.

# What To Do Instead

# Start with spreadsheets — that's correct

For the first 3-6 IBP cycles, spreadsheets are the right choice. They let you iterate on the process design without the overhead of a tool implementation. See Technology Before Process for why this sequencing matters.

# Set a graduation trigger

Define upfront when you'll outgrow spreadsheets. A reasonable trigger: when the process runs across 3+ product families, involves 3+ functions, and has completed 3+ cycles. At that point, the process is proven and the pain of manual management starts to outweigh the simplicity.

# Graduate, don't leap

Moving off spreadsheets doesn't require a $500K planning platform. The progression can be gradual:

Stage	Tool	When
1. Launch	Excel / Google Sheets	Cycles 1-6
2. Stabilize	Shared workbook on SharePoint/Teams with access controls	Cycles 6-12
3. Structure	Simple database or BI tool (Power BI, Tableau) for reporting; spreadsheet for input	Cycles 12-18
4. Scale	Purpose-built planning tool	When process maturity and business case justify it

# Document institutional knowledge now

Don't wait until migration to document how the spreadsheets work. If only one person understands the model, the process is fragile regardless of the technology:

Document data sources, refresh procedures, and key formulas
Cross-train at least one backup analyst
Separate data input from calculation from presentation

# Warning Signs

You might be in this anti-pattern if:

Only one person understands the "master spreadsheet"
Meeting prep takes longer than the meeting itself
The demand plan lives on someone's personal OneDrive or desktop
Version conflicts are a recurring issue ("whose numbers are these?")
Scenario analysis is avoided because it's too hard to model
The spreadsheet has grown beyond 30 tabs or 10MB
New product families or regions are resisted because "we'd have to rebuild the model"

# Further Reading

Technology Before Process — The opposite extreme: buying a tool before understanding the process.
Data Foundations — Understanding data requirements helps design more sustainable spreadsheet models.
Maturity Model — Technology adoption mapped to process maturity levels.

anti-pattern