Customer concentration: how much is too much when you sell?

What is customer concentration?

Customer concentration means a large share of your revenue comes from a small number of customers, often just one. Buyers and lenders treat it as a risk because losing one of them could take a big piece of the income they are paying for.

Why buyers care

A buyer is paying today for income they expect tomorrow. If a third of that income depends on one customer's goodwill, the buyer is taking a bet on a relationship they do not have yet. And that relationship is often with you.

Lenders feel the same. Those financing a purchase may ask about a large customer and what would happen if that customer left. If the buyer borrows through the Small Business Administration (an SBA 7(a) loan), is new to the business, and the business price, not counting owner-occupied real estate, is $3 million or more, the lender must get a quality of earnings report: an independent professional's check of whether the profit is real and would carry over to a new owner. Since October 1, 2026, SBA says that report must look at how dependent the business is on a few customers and whether their contracts will continue (SBA SOP 50 10 8.1, Appendix 15). Below that size, lenders still check the numbers, so ask the buyer's lender how it applies.

How much is too much?

There is no official limit, and advisors give different numbers. A business broker writing on Divestopedia says buyers are typically concerned when one customer is more than 10% of revenue. A broker writing for Keystone CPAs uses a customer at 30% of revenue as an example of real cash flow risk. Treat both as rules of thumb.

Share of revenue is only a starting point. A buyer wants to know how much profit would go if the customer left, and how likely that is. The same Divestopedia article notes that losing a low-margin customer may not hurt the bottom line much.

Roughly, buyers react like this:

If your largest customer left tomorrow	How buyers tend to react
Profit would barely move	Little concern. They will still ask about the customer's history
Profit would drop, but the business would carry on	Questions about the contract and who handles the account. Some will offer less or want protective terms
Profit would fall sharply, or costs would no longer be covered	A serious issue. A buyer is likely to want a lower price or protective terms, and some buyers and lenders may pass

Look at your top five together too. If a few customers make up most of your revenue, buyers tend to ask the same questions.

How does customer concentration affect the price?

An illustration with round numbers, not a valuation: a made-up business earns $400,000 a year and would sell for about two and a half times earnings ($1,000,000). Its largest customer's work produces $150,000 of those earnings.

A buyer who trusts the customer pays the full multiple on all of it. At two and a half times, that $150,000 supports $375,000 of the price, so it is the part a buyer is most likely to want protected. A buyer who doubts the customer might pay less for that part. Say the buyer would pay half the usual multiple for it. This is an assumption for illustration, not a typical discount. The price would fall by $187,500, from $1,000,000 to $812,500. Or the buyer might pay for that part only if the customer stays, which is an earn-out (see below). See what is my small business worth? for how the multiple is set.

How it changes the terms

Buyers often protect themselves instead of walking away:

• A lower price. A buyer may pay a lower multiple of earnings because those earnings feel less safe. Some keep the price and put the risk into the terms instead.
• An earn-out. Part of the price is paid later, only if the customer stays. SBA's rules prohibit seller earn-outs on 7(a) loans that fund a business purchase, so a seller earn-out isn't available if the buyer uses one. See what is an earn-out?.
• A longer handover. A buyer may ask you to stay on longer so the customer relationship moves to them. If the buyer uses a 7(a) loan, you generally can't stay on as an officer, director, stockholder or employee, but the business can hire you as a consultant for no more than 24 months in total.
• Seller financing. You lend the buyer part of the price, so you share the risk. See seller financing.

None of these is necessarily bad. But you want to choose them, not have them forced on you.

Work out your own numbers first

Export three years of sales by customer and work out:

1. Your largest customer's share of revenue and, roughly, of profit, each year
2. Your top five customers' share of revenue, each year
3. How many years each of your top ten has been buying from you
4. What share of last year's revenue came from customers who also bought the year before

You may be surprised, in either direction. Know your numbers before a buyer finds them.

If you have a year or more

• Grow the rest. You don't need to shrink the big customer. Growing other accounts brings the percentage down. The same Keystone post gives the example of taking a 30% customer down to 18% or 20% of revenue this way.
• Get a contract. A multi-year agreement with your largest customer gives a buyer something firmer to rely on. Check that it survives a change of ownership, and have your lawyer read it.
• Widen the relationship. Make sure several people at your business know several people at theirs. See how to make your business run without you.

If you are selling soon

The numbers won't change quickly, so show a buyer why the risk is lower than the raw figures suggest:

• Show the history. A customer who has bought every month for fourteen years is not the same risk as one who arrived last spring. Put the tenure in front of the buyer.
• Show why they stay. Are you the only approved supplier? Would switching be costly or slow for them? Say so, specifically.
• Show it isn't personal. If your operations manager already handles the account day to day, that shows the relationship doesn't rest on you alone, which helps more than argument does.
• Offer the introduction. Plan how and when the buyer meets the customer, with your endorsement. Usually late in the process, under confidentiality.
• Be open about it early. A buyer who hears about a big customer in the first conversation can price it in. One who finds it later, during due diligence (their detailed check of your records), is more likely to reopen the price or the terms. Raise it before you sign the letter of intent, the document that sets out the price and main terms ahead of the final contract.

If your biggest customer is under contract

Check whether the contract can be ended on short notice and whether it can pass to a new owner. A federal government contract generally can't be transferred without the government's agreement, a step called novation (Federal Acquisition Regulation 42.1204). If the buyer buys the company's shares, the contract holder doesn't change and novation may not be needed. If the buyer buys the business's assets, the government has to agree to the switch. State, city and school contracts follow their own rules. Have your lawyer read the contract before a buyer does.

The other kinds of concentration

A single supplier you depend on, a single salesperson who brings in most of the work, or a single referral source raises similar questions, and some of the same fixes help, such as a written agreement and a second person who knows the relationship.

What to do first

Run the four numbers above for your own business. If your largest customer's share worries you and a sale is a year or more away, start on that list now and build it into your exit plan. If you are selling soon, start with the list for selling soon.

Keep reading

• What is an earn-out when you sell your business?
• What is my business worth? How to value a business for sale
• How to make your business run without you

This guide is general information, not tax, legal or valuation advice. Every business is different: talk to your accountant, lawyer and broker about yours.