Customer concentration is the share of revenue from your largest customer, and from your top five. Buyers start a detailed review when one customer passes 20% of revenue. Above 30%, some buyers decline outright (FOCUS Investment Banking). Early on the bar is looser. Lighter Capital's rule for SaaS companies at $200K ARR or less is that no single customer should exceed 50%. Measure at the parent company, show the trend every quarter, and grow around the big account rather than shrinking it. Not legal, tax, or investment advice.
This page covers revenue from your largest customers. For how much of that revenue you keep each year, use NRR vs GRR for the board pack. For what goes in the data room, use the Series A diligence checklist.
How to measure customer concentration
| Measure | Formula | Rule |
|---|---|---|
| Largest customer share | Revenue from your largest customer ÷ total revenue, same period | Lighter Capital |
| Top-five share | Revenue from your top five customers ÷ total revenue, same period | Lighter Capital |
| Who counts as one customer | Entities under common control count as one. The federal government counts as one, and so does each state, local, or foreign government | ASC 280-10-50-42 |
| Public disclosure line | Any single customer at 10% or more of revenue | ASC 280-10-50-42 |
Use trailing twelve months of revenue, or ARR, and keep the same choice in the deck, the model, and the board pack. Roll up the subsidiaries before you report. Three business units of one parent are one customer under ASC 280, and a buyer's diligence team will roll them up too.
ASC 280 applies to public companies. It is still a useful line for a private one. If a customer is big enough that a public company would have to disclose it, it belongs on your board slide.
Where the lines sit, by source
| Share from one customer | What the source says | Source |
|---|---|---|
| Above 50% at $200K ARR or less | Too risky for an early SaaS company | Lighter Capital |
| Above 10%, or above 25% for the top five | You may have high concentration | Lighter Capital |
| 10% or more | Public company must disclose the customer | ASC 280-10-50-42 |
| Above 20% | Catches a buyer's eye and triggers a detailed review | FOCUS Investment Banking |
| 20–25% | Standard diligence risk flag | Glacier Lake Partners |
| Above 30% | More buyers decline the deal outright | FOCUS Investment Banking |
| Above 40% | Lenders lend less against the deal, and some buyers want a customer estoppel letter | Glacier Lake Partners |
Lighter Capital adds a floor for the earliest stage: at least 4 customers by $100K ARR. FOCUS and Glacier Lake write about sales of lower middle market companies, many outside software. Treat their lines as what a buyer will ask, not as a venture benchmark.
There is no reliable public benchmark yet for largest-customer share at Seed to Series B. Burkland lists extreme revenue concentration with no diversification plan as a Series A red flag, with no number attached. Expect the question at any share, and have the trend and the plan ready.
What concentration does to a raise and a sale
FOCUS names four effects on a sale: a lower price, perhaps 20–35%, fewer buyers, terms that shift risk to the seller through escrow, earnouts, and warranties, and a longer close. Glacier Lake adds that buyers use concentration after the letter of intent to argue for escrow or an earnout, even when it was disclosed up front.
Buyers usually take the risk back through the earnout. SRS Acquiom's 2026 Deal Terms Study covers more than 2,300 private-target deals that closed from 2020 through 2025:
| Earnout measure (non-life-sciences deals) | 2025 | Source |
|---|---|---|
| Deals with an earnout (excluding life sciences) | 24% (22% in 2024, 33% in 2023) | SRS Acquiom 2026 |
| Median earnout potential as a share of the closing payment | 34% | SRS Acquiom 2026 |
| Median earnout length | 21 months | SRS Acquiom 2026 |
| Payout across all deals with earnouts | About 21 cents per dollar | SRS Acquiom, 2024 Claims Insights |
Plan around the payout row. A dollar of price moved into an earnout has paid about a fifth of a dollar on average. For deals with any earnout payout, SRS Acquiom reports about half the maximum gets paid.
A raise works the same way, one step earlier. Lighter Capital's investor question is "what happens to your business if a client doesn't renew?" Answer it with contract length, renewal terms, the customer's spend trend, and a reference call.
The VEN (Venture Executive Network) session judgment matches the sale data. Concentration rarely kills an exit. It changes the structure, from all cash at close toward an earnout. The buyer's first question is whether the big customer stays if the founder leaves.
Labeled example
Editorial arithmetic. Not a company and not a market rate.
You have $3.0M in ARR. Your largest customer pays $900K, or 30%. Over twelve months you add six customers at $150K each, and the large account stays flat.
| Scenario | Largest customer | Total ARR | Largest customer share |
|---|---|---|---|
| Today | $900K | $3.0M | 30% |
| Six new $150K customers, large account flat | $900K | $3.9M | 23% |
| Same, large account grows 10% | $990K | $3.99M | 25% |
| Large account churns today | $0 | $2.1M | ARR falls 30% |
Adding customers moves the share faster than cutting the big one, and you keep the revenue. The last row is the case a buyer or lead investor will model. Have your answer to it.
How to lower the risk before a raise or a sale
Customer concentration before the next round
- Report it monthly. Largest customer share and top-five share, rolled up to the parent, on the board slide.
- Show three years of trend. A falling share with the big account still growing reads very differently from a rising one.
- Read the big contract. Term, renewal, termination for convenience, and change of control. Missing or lapsed contracts turn into escrow (Glacier Lake).
- Add relationship owners. Glacier Lake: if you are the main contact for your top three customers, diligence will find it. Name an owner below you for each of the top five.
- Write the plan to grow around it. Name the next accounts in the same segment and when they close.
- Line up a reference. A call with the big customer's decision maker answers the renewal question better than a slide (Lighter Capital).
- Price the earnout before you need to. If a buyer offers one, ask for the metric, the period, and the reporting rights in writing.
Mistakes founders make with a big customer
Counting subsidiaries as separate logos. ASC 280 rolls entities under common control into one customer. A buyer will too.
Showing top-one share without top five. Five customers that make up half the revenue carry risk even when none passes 20%.
Treating it as a sales problem only. FOCUS lists a key manager leaving and taking the customer as one way concentration turns into lost revenue. Spread the relationship across your team.
Taking an earnout at face value. Price it at what earnouts have paid, not at the maximum (SRS Acquiom).
Pair this with
- NRR vs GRR for the board pack for the retention slide beside the concentration slide.
- Series A diligence checklist for the rest of the data room, including customer contracts.
- When to raise a Series A for the other red flags investors check.
- How to negotiate your first customer contract to set renewal and termination terms before the account gets big.
Sources
- FOCUS Investment Banking, The Perils of Customer Concentration in M&A. Craig Ladkin, 17 July 2025. Above 20% of sales triggers a detailed buyer review; above 30% more buyers decline; above 40% the rest of the picture must fit well; valuation reduced perhaps 20–35%; fewer buyers; escrow, earnout, and warranty terms shift to the buyer; longer close; a top manager leaving with the customer as a risk.
- Glacier Lake Partners, What Buyers Find in Every Lower Middle Market Diligence. 3 August 2025. Single-customer share above 20–25% is a standard diligence flag; above 40% lenders cut the debt they will provide and some buyers want a customer estoppel letter; concentration used after the letter of intent to argue for escrow or an earnout; missing contracts create escrow; founder as main contact for top customers.
- Lighter Capital, How to Minimize Your SaaS Startup's Customer Concentration Risk. 28 July 2023, updated. Concentration formula; more than 10% from one client or 25% from the top five may be high; at $200K ARR or less no customer above 50%; at least 4 customers at $100K ARR; investor renewal question; contract length, spend trend, and reference call.
- Deloitte DART, Information About Major Customers (ASC 280-10-50-42). Public entities disclose any single external customer at 10% or more of revenue; entities under common control count as one customer; each government counts as one customer.
- SRS Acquiom, 2026 M&A Deal Terms Study (PDF). More than 2,300 private-target deals closed 2020 through 2025; earnouts in 24% of 2025 non-life-sciences deals, 22% in 2024 and 33% in 2023; median earnout potential 34% of the closing payment; median length 21 months.
- SRS Acquiom, M&A Deals: Key Trends from the 2025 Deal Terms Study. Citing the 2024 M&A Claims Insights Report: earnouts pay about 21 cents on the dollar across deals with earnouts, excluding life sciences; about half the maximum paid where any payout occurs.
- Burkland, How Investors Evaluate Series A Startups in 2026. 21 July 2026. Red flags include extreme revenue concentration with no diversification plan.
- VEN (Venture Executive Network). Founder sessions on customer concentration, 2026. Concentration rarely kills an exit; it changes the structure from all cash toward an earnout; buyers ask whether the big customer stays if the founder leaves. Not a survey. No closed-session numbers.
Related
- Finance, metrics & runway
- NRR vs GRR for the board pack
- Series A diligence checklist
- When to raise a Series A
- How to negotiate your first customer contract
- Monthly investor update template
Founders who have raised or sold with one customer carrying the revenue will pressure-test your concentration slide and your plan to grow around that account in a VEN session.
Go deeper: VEN playbook note on customer concentration