Customer concentration risk is the business risk of being too dependent on a small number of customers for revenue. If your top 3 customers represent 70% of ARR, losing one is not just a sales setback — it's a potential solvency issue.
Investors, acquirers, and lenders evaluate concentration risk in every due diligence process. Understanding their thresholds helps you proactively manage the risk.
The investor perspective
When VCs and PE firms evaluate a SaaS company, customer concentration is one of the first things they look at. Here's why:
Revenue predictability: Concentrated customer bases are inherently less predictable. The top customer decides to consolidate vendors, and your ARR drops 25% overnight. Diversified customer bases have smoother, more predictable revenue.
Negotiating leverage: A customer representing 30% of your ARR has enormous leverage in contract renewals. They can demand lower pricing, better terms, and more customization — compressing your margins.
Exit risk: M&A buyers heavily discount companies with high concentration. The acquirer inherits the same risk, and they price accordingly.
Industry benchmarks
| Company stage | Typical max single customer | Typical top-5 max |
|---|---|---|
| Pre-seed / Seed | 30–50% (often 1–2 enterprise customers) | 80–90% |
| Series A | 15–25% | 50–70% |
| Series B+ | 5–15% | 30–50% |
| Pre-IPO / Public | 5–10% | 20–30% |
Early-stage companies almost always have concentration issues — that's expected. What investors look for is a trajectory toward diversification as the company grows.
When concentration is acceptable
High concentration is more acceptable when: - The concentrated customer has a long contract (3+ year term) - NRR from that customer is very high (expanding, not contracting) - You have signed Letters of Intent or renewals - The customer is a publicly traded company with stable finances
It's less acceptable when: - The customer is a single-stakeholder relationship (leaves if the champion leaves) - They're on month-to-month contract - They've signaled pricing sensitivity or potential vendor consolidation
The HHI as a concentration score
The Herfindahl-Hirschman Index (HHI) is a single number summarizing concentration. It squares each customer's revenue share (as a decimal) and sums them, × 10,000.
HHI for a perfectly equal 10-customer split: (0.1)^2 × 10 × 10,000 = 1,000 HHI for a 50% + 10 equal customers split: 0.5^2 × 10,000 + 9 × (0.056)^2 × 10,000 ≈ 2,780
Below 1,500 = healthy diversification. Above 2,500 = high concentration.