The Forecast That Smiled While the Business Bled: A Case of One 'Big Customer'
Why a smooth revenue curve is often a mask for dangerous customer concentration, and how to use scenario bands to see the cliff edge.
The Paper Chair
Come, stand next to me and look at this projection model. It is beautiful, is it not?
Look at the blue line representing “Projected Revenue.” It climbs steadily from January to December, rising at a polite 4% month-over-month. It is smooth. It is confident. It tells us that by Q4, we will be hiring three new engineers and moving into a larger office.
But this chart is lying to us. It is a paper chair—it looks like furniture, but if you sit on it, it will collapse.
The Distortion: This forecast assumes that “Revenue” is a homogeneous liquid, like water filling a tank. It assumes that every dollar behaves the same way and carries the same risk. But when we aggregate revenue into a single total, we hide the structural integrity of the business. We are looking at the roof, but we have not checked the pillars.
The Signal: We must dissolve the aggregate. When we break this blue line down by “Customer Name,” the smooth curve disintegrates.
Look at what remains. We see a chaotic mess of small, noisy contracts at the bottom… and then, floating above them like a dark cloud, is Client Alpha. Client Alpha contributes $45,000 of the $70,000 monthly total.
The smooth growth you saw? That was just Client Alpha adding a few seats. The stability you felt? That was Client Alpha renewing a contract. The entire company is not a business; it is a project management office for Client Alpha.
Here is the composition of the stated monthly total. A full time series is not supplied, so this view shows one month’s concentration rather than inventing an area-chart history:
MONTHLY REVENUE: $70,000
[AAAAAAAAA|ooooo]
Each letter = $5,000
A = Client Alpha: 9 x $5,000 = $45,000
o = Other clients: 5 x $5,000 = $25,000
REMOVE ALPHA'S SEGMENT FOR THE LOSS SCENARIO
[ooooo]
Remaining revenue: $25,000| Scenario | Monthly revenue | Share of the original total |
|---|---|---|
| Client Alpha retained | $70,000 | 100.0% |
| Client Alpha removed; other revenue unchanged | $25,000 | 35.7% |
| Revenue removed with Alpha | $45,000 | 64.3% |
This cut reveals the dependency. Whether the remaining business has negative cash flow depends on its costs and collection timing, which this revenue split does not supply.
Removing the Crystal Ball
We do not guess the future; we project the trend. But we must project all the trends, not just the happy one.
To fix this dishonesty, we must stop showing the Single Line Forecast. The Single Line is arrogance. It implies we know exactly what will happen. We do not.
Instead, we will build a Scenario Band.
Open your spreadsheet. We are going to create a new row called “The Cliff.” In this row, we simulate the immediate loss of our largest customer in Month 3.
When you plot this, the chart changes. You no longer have a single line pointing to the moon. You have a fork in the road.
- Path A (Status Quo): We grow gently.
- Path B (The Cliff): We lose Client Alpha’s revenue. Compare the remaining cash receipts with outflows to see whether cash flow turns negative.
This visual is violent. It is uncomfortable. But it is the truth.
The Shape of Safety
When you present this to your team, the mood will shift. The celebration of the “Average Growth” will stop. The conversation will turn to the real work: “How do we widen the base?”
We need to hunt for the Barnacles (smaller, diversified revenue) to build a floor that can catch us if the Whale falls. Until the revenue from the small clients can cover the operating expenses, we are not safe.
Do not let the smooth curve sedate you. Force the spreadsheet to show you the worst case, so you can build a business that survives it.
FAQs
Why is having a big customer bad?
It is not bad to have them; it is bad to rely on them. If they pay the rent, they own the building, not you.
How do I show this in a forecast?
Do not use one line. Use bands. Show a 'Base Case' and a 'Churn Event' case side-by-side.
My board hates negative scenarios. What do I do?
You tell them that ignoring the cliff does not build a bridge over it. Transparency is the only safety.