# Customer concentration: when one big customer becomes a risk

> Customer concentration risk in a small SaaS: measure one customer’s share of MRR, stress-test losing them and shape a big deal so it stays safe.

- Source: https://productovi.com/blog/customer-concentration-risk
- By: Sergey Bruh
- Published: 2026-09-30
- Topics: Price changes and big customers, MRR, churn and retention, Valuation

**Customer concentration** is how much of your revenue depends on your largest customers. It becomes a risk when losing one of them would push the business into a loss or force it to change course, usually once a single customer passes 10–20% of monthly recurring revenue, or earlier if you've built custom work just for them. To judge a big deal, calculate the customer's share of MRR, then stress-test the month after they leave: revenue without them against the costs you'll still have. Below is one offer worked through, with three ways to answer it.

## An offer that looks like a gift

Denys and Olha run FitRota, a web app for independent fitness studios: class schedules, memberships and reminders. **120 studios pay 800 UAH a month**, so MRR is 96,000 UAH. Costs are 80,000 a month: 70,000 for the two founders' pay and 10,000 for tools, SMS and an accountant. Profit: **16,000 UAH a month**.

A national chain of 50 studios gets in touch. Their proposal:

- all 50 studios, but at **600 UAH per studio**: 30,000 a month;
- an integration with the chain's own door-access system, and the app in the chain's colours;
- a 12-month contract.

The integration is more than the founders can build and maintain themselves, so they would hire a contract developer for **25,000 UAH a month** with three months' notice.

## Step 1. The share of MRR

$$
\frac{30\,000}{96\,000 + 30\,000} = \frac{30\,000}{126\,000} \approx 23.8\%
$$

Almost a quarter of revenue from one customer. For comparison, today FitRota's biggest customer, an owner with two studios, pays 2 × 800 = 1,600 UAH: 1.7% of MRR.

## Step 2. The month after they leave

With the chain, profit becomes 126,000 − (80,000 + 25,000) = **21,000 UAH**, only 5,000 more than today, because the custom work eats most of the extra revenue.

Now suppose the chain leaves when the contract ends: a new manager, a merger, a cheaper supplier. The developer is still on notice for three months:

$$
96\,000 - 105\,000 = -9\,000 \text{ UAH a month}
$$

Three months of losses, 27,000 UAH in total, plus integration code that nobody else needs and somebody still has to maintain or remove. In exchange for a year of 5,000 UAH extra profit a month, the founders would take on a real chance of losing money after it.

There's a quieter cost too. While the chain pays a quarter of the bills, every one of its requests jumps the queue, and the product drifts toward one customer's needs instead of the 120 studios that chose it.

## Three ways to answer

| Option                                                     | Share of MRR | Monthly profit with the chain, UAH | Monthly profit if the chain leaves, UAH |
| ---------------------------------------------------------- | ------------ | ---------------------------------- | --------------------------------------- |
| A. Accept as offered: 50 × 600, custom work, contractor    | 23.8%        | 21,000                             | −9,000 during notice, then 16,000       |
| B. Standard product, 650 per studio, start with 15 studios | 9.2%         | 25,750                             | 16,000                                  |
| B, after all 50 studios have joined                        | 25.3%        | 48,500                             | 16,000                                  |
| C. Decline                                                 | —            | 16,000                             | 16,000                                  |

How option B is calculated: 15 × 650 = 9,750 UAH, so MRR is 105,750 and the share 9,750 / 105,750 ≈ 9.2%. With no custom work, costs stay at 80,000, so profit is 25,750. If all 50 studios join, 50 × 650 = 32,500, and profit is 128,500 − 80,000 = 48,500.

Option B is the founders' answer: the standard product at a volume price, no custom integration, a gradual rollout starting with 15 studios. By revenue share, the fully rolled-out option B is as concentrated as option A. The difference is the downside: if the chain leaves, FitRota is back where it started, not in a loss. **Concentration risk is revenue share multiplied by how much of your cost base and roadmap depends on that customer.**

![Option A puts 23.8% of MRR on one customer with custom work and a loss if they leave; option B reaches a similar 25.3% but stays survivable, because profit falls back to 16,000 UAH rather than below zero](/blog/customer-concentration-risk/diagram.png)

The chain may say no to 650. That's a fine outcome too: FitRota keeps its current, healthy business.

## How to make a big customer safer

- **Standard product only.** Custom work creates costs that stay after the customer leaves.
- **Grow the rollout in stages.** Start with a part of the chain; add studios as they succeed.
- **Ask for payment upfront.** A year paid in advance turns the contract into cash, not a promise.
- **Keep selling to everyone else.** The only lasting cure is a bigger base of normal customers.
- **Watch the share every month.** Add "largest customer, % of MRR" and "top five, % of MRR" to your monthly numbers, next to [MRR and churn](/blog/how-to-calculate-mrr-and-churn).

## Why concentration lowers what your company is worth

Anyone who considers buying or investing in your company will ask for revenue by customer. A business where one customer brings a quarter of the revenue is judged partly as a bet on that customer, and the price usually falls or part of it becomes conditional on the customer staying. More on how buyers value small SaaS companies: [how much a small SaaS business is worth](/blog/how-much-is-a-saas-business-worth).

## Why small niches invite this problem

In a niche with a few hundred possible customers, one chain can look like a shortcut to the next milestone. Before taking it, check whether the normal market is big enough to reach your goals without it; [bottom-up market sizing](/blog/bottom-up-market-sizing) shows how. If it is, the big customer is a bonus, not a lifeline, and you can afford to say no to bad terms.

## Common mistakes

- **Looking only at revenue.** The share of MRR matters less than the costs and commitments that come with it.
- **Discounting deeper for size.** A large customer at a low price plus custom work can earn less than a few small ones.
- **Promising the roadmap.** "We'll build it for you" is a cost you pay long after the invoice.
- **Not measuring.** Concentration creeps up; it is easy to miss without a monthly number.

## Key takeaways

- Measure the largest customer's share of MRR and the top five's share every month.
- Stress-test the month after a big customer leaves, including costs you can't cut quickly.
- Offer the standard product, a volume price and a staged rollout instead of custom work.
- Concentration lowers what the company is worth to a buyer, so it matters even if the customer never leaves.

## FAQ

### What is customer concentration risk?

It is the risk that losing one customer, or a few, would seriously damage the business. It grows with that customer's share of revenue and with the costs and product decisions made for them.

### What share of revenue from one customer is too much?

A common rule of thumb is that more than about 10% of revenue from one customer draws questions from buyers and lenders, and more than 20–25% is a serious risk. For a small company, the stress test matters more than the exact threshold.

### Should a small SaaS ever accept a very large customer?

Yes, on terms that leave you safe if they leave: standard product, a fair volume price, a staged rollout and ideally payment in advance.

### How do I reduce customer concentration I already have?

Grow the rest of the customer base faster than the big customer, avoid new custom commitments, and negotiate longer contracts or annual prepayment with the largest customer while the relationship is good.

## Learn it hands-on

The lesson [One customer too big](/courses/bootstrapped-product/one-customer-too-big/theory) follows two founders when a franchise asks for a special deal, with numeric exercises and a case checked by AI. It is part of the course _From Idea to Profitable Product: Building Without Investors_; the lesson [What the business is worth](/courses/bootstrapped-product/what-the-business-is-worth/theory) shows how buyers look at the same numbers.

## Related lessons

- [Revenue concentration: one customer too big](https://productovi.com/courses/bootstrapped-product/one-customer-too-big.md)
- [MRR calculation and monthly churn](https://productovi.com/courses/bootstrapped-product/mrr-and-churn.md)
- [Raising prices without losing customers](https://productovi.com/courses/bootstrapped-product/raising-the-price.md)
- [How much is the business worth?](https://productovi.com/courses/bootstrapped-product/what-the-business-is-worth.md)
- [How to sell a business: the deal](https://productovi.com/courses/bootstrapped-product/the-deal.md)