Quick answer: Customer due diligence is the buyer’s test of whether the revenue it is paying for will still be there after closing. Buyers read the largest contracts for term, termination, change-of-control and pricing clauses, rebuild retention by customer cohort from invoice data, review credits and disputes, and call the biggest customers late in the process, usually with the owner’s consent. Findings reach the deal as a lower price, an earnout, an escrow or a closing condition.
Key points
- Buyers confirm customer revenue in a fixed order, starting with the revenue schedule, then the contracts and finally the customers themselves.
- Retention measured from invoices is stronger evidence than a description of loyalty, because it shows what each group of customers did.
- Change-of-control and assignment clauses are read first, because they decide whether a contract moves to the buyer without the customer’s consent.
- Customer calls usually follow the letter of intent, and the owner and advisor negotiate who is called, in what order and with what introduction.
Customer diligence tests revenue that has not happened yet
A buyer pays for sales it expects after closing, so customer diligence asks whether each major customer will keep buying on the same terms under a new owner. The test covers whether the revenue is contractual or only habitual, whether the contract survives the change of owner, whether the price will hold and whether the customer is satisfied.
The evidence arrives in a set order. A customer-level revenue schedule comes first, then contract review, then retention and pricing analysis from invoice data, then credits and disputes. Customer calls come last. The diligence overview places this work among the other workstreams, and the customer concentration guide covers how buyers price dependence on a few accounts, which this page does not repeat.
The schedule shows revenue by customer and month for every period under review. The buyer’s accountants compare its total with the general ledger and list each gap, because a schedule that does not reconcile makes buyers doubt every customer statistic from the same system. They group customers that decide together, such as a parent and its subsidiaries, set apart sales to businesses the owner also owns, and ask for a log of lost customers with the reason for each. A seller who can document each departure is more credible than one who says customers rarely leave.
Contract review: the clauses that decide what transfers
Buyers read the largest customers’ contracts against a fixed list of clauses, and deal structure changes which ones matter. In an asset sale a contract generally has to be assigned to the buyer. In a stock sale it stays with the company, but a change-of-control clause can still give the customer a right to act, as the comparison of asset and stock sales explains.
| Clause | What the buyer reads for | Where a problem shows up |
|---|---|---|
| Term and renewal | A fixed term, automatic renewal, or purchase orders with no commitment | The share of revenue treated as recurring, and so the multiple |
| Termination | Termination for convenience, short notice, rights triggered by a change of owner | Earnout, holdback or lower price for revenue that can be cancelled |
| Assignment and change of control | Whether the customer must consent to a transfer or may end the contract on one | Consent as a closing condition, or price held back until it arrives |
| Pricing | Fixed price, escalators, resets, most-favored-customer clauses, rebates | Forward margin and adjusted EBITDA |
| Exclusivity | Promises not to serve competitors, territory limits, clauses that could reach the buyer’s other businesses | Deal structure, or a request for a waiver |
| Service levels | Credits for late delivery or downtime, warranty terms, liability caps | Reserves, specific indemnities and escrow size |
| Missing or expired paper | No signed contract, or an agreement that lapsed and continues by habit | Revenue treated as uncontracted until the paper is fixed |
The last row is the one owners underestimate. A customer that has bought for years on purchase orders is valuable, but the buyer cannot read a termination right in a document that does not exist, so it prices the relationship at its weakest reading. A seller can prepare a one-page abstract for each major contract with the signed copy and amendments, the renewal date, the termination and assignment language quoted exactly, and the pricing mechanism, which shortens the buyer’s review. Liability caps, indemnities and the rest of each agreement belong to the legal diligence review.
Retention and pricing: what customers actually did
A customer list cannot show how much of last year’s revenue is still here. Retention analysis can. Buyers group customers by the period in which each first bought, called a cohort, and follow each group’s revenue forward. Gross retention counts only what existing customers kept, capping each at its earlier spend so that growth in one account cannot hide a loss in another, and net retention includes that growth. A company can report rising revenue and a net retention below its starting base, which means new customers are replacing a base that shrinks each year. Project businesses use the share of each year’s revenue from customers who also bought the year before.
Illustrative example: Reading a cohort table
A company reports revenue by the year each customer group first bought.
| Customer group | Year 1 | Year 2 | Year 3 |
|---|---|---|---|
| On the books at the start of year 1 | $4,000,000 | $3,400,000 | $3,100,000 |
| First bought in year 2 | none | $2,000,000 | $1,900,000 |
| First bought in year 3 | none | none | $1,500,000 |
| Total revenue | $4,000,000 | $5,400,000 | $6,500,000 |
Revenue grew from $4,000,000 to $6,500,000, which looks strong. The oldest group kept 85 percent of its year 1 revenue in year 2 and about 91 percent of its year 2 revenue in year 3. Customers on the books at the start of year 3 spent $5,000,000 that year against $5,400,000 the year before, a net retention of about 93 percent. New customers supplied $1,500,000, which is 23 percent of year 3 revenue and more than all of the net growth, so a buyer will ask what that revenue cost to win. The figures are invented to show the mechanics and are not benchmarks.
Price is tested alongside volume. Buyers split revenue change into price, volume and mix, then ask when prices rose, by how much and what each customer’s orders did afterward. They also compare each large customer’s net price after rebates and credits with its list price, since a net price that drifts down means the customer is renegotiating without signing anything.
Credits and disputes are read as a set, because one credit memo means little and a run of them at one customer means a relationship under pressure. Buyers review credit memos and returns by customer and month, especially just after a period closes, as the revenue recognition review also does. They also review disputed invoices, aged receivables, warranty claims and price concessions granted in the last few months, which a buyer treats as an early sign of the new run rate.
A plan for customer calls
Calls are the one step in which the buyer hears the customer directly, so both sides treat them as a controlled event. They usually come after the letter of intent, when a price is agreed and exclusivity is in place, so the seller exposes its customers to one committed buyer and not to a field of bidders. Where a few accounts carry the business, a buyer may make the largest customer’s consent or confirmation a condition of closing.
| Stage | What happens | Who decides |
|---|---|---|
| Before launch | The seller ranks customers by revenue and profit, notes who owns each relationship and decides which could be contacted at which stage | Owner and advisor |
| Request and selection | The buyer asks for the largest customers, a sample of mid-size ones and sometimes a lost account, and the parties agree who is called and in what order | Buyer, owner and advisor |
| Preparation | The owner speaks with each customer first, explains the transaction and the reason for the call, and says who will phone and when | Owner |
| The call | The buyer or its advisor asks about the relationship under agreed ground rules | Buyer |
| Follow-up | The buyer writes up what it heard, and the owner speaks with the customer again if a concern surfaces | Buyer and owner |
A buyer asks why the customer buys from this supplier and what else it considered, how the company compares on quality, delivery, price and service, whether anything would change if the owner left, whether volumes will grow or shrink, and how the customer would feel about a new owner.
Buyers often ask that the owner stay off the call, and sellers often ask that their advisor listen in, so the ground rules settle both. A scripted customer is easy to spot, and coaching answers damages the one source of evidence buyers trust most. The better preparation is factual, covering who is buying, why the owner is selling, that service continues and what the customer should expect. The guide to telling customers about a sale covers the announcement itself. When the buyer is a competitor, customer names and prices are often held back until late or shown only to outside advisors.
How customer findings reach price and terms
Findings land in four places. A weak retention record lowers the revenue base the buyer projects and, with it, adjusted EBITDA or the multiple. A contract that can be cancelled, or a customer likely to leave, moves part of the price into an earnout, holdback or escrow, which the earnout guide explains. A consent requirement becomes a closing condition, and a dispute or warranty exposure becomes a specific indemnity.
The later a finding arrives, the weaker the seller’s position. A seller who runs the same analysis first, as part of a sell-side quality of earnings review, hears the issue while there is time to answer it. Patterns that span several customers also appear in the guide to red flags buyers find.
Frequently asked questions
When do buyers contact a seller’s customers?
Usually late, after the letter of intent and often close to signing, once the buyer is committed and the seller has agreed who may be called. Buyers start with the largest customers by revenue and profit. Some deals include few calls or none, particularly where the customer base is diversified.
Can a seller refuse to let a buyer speak with customers?
A seller can negotiate who is called, when and under what ground rules, and buyers usually accept limits. A flat refusal tends to be read as a sign that the revenue will not hold. The buyer may then discount the revenue it cannot verify or make closing depend on the customer’s written confirmation.
Which customer contract terms matter most to a buyer?
Change-of-control and assignment clauses come first, because they decide whether the contract moves without consent. Termination rights come next, since a customer that can leave on short notice makes revenue less certain. Term, renewal and pricing mechanisms follow. A missing or expired contract leaves the buyer nothing to rely on.
What is a customer retention analysis?
It groups customers by the period they first bought and follows each group’s revenue in later periods. Gross retention counts only what existing customers kept, while net retention includes growth inside retained accounts. Buyers build it from invoice data, so it shows what customers did and not what the seller expects them to do.
What if a major customer has no written contract?
The revenue still counts, but the buyer treats it as uncontracted and may price it as higher risk, move part of the price into an earnout or ask for a signed agreement before closing. Order history, correspondence and pricing records help document the relationship, and a seller can ask the customer to sign before launch.
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Related guides
- Customer Concentration and Valuation: How Buyers Price the Risk: Why buyers pay less for businesses that depend on a few customers, how they measure concentration, and what owners can do to reduce the discount before a sale.
- Revenue Recognition Due Diligence: Where Buyers Find Problems: How buyers test when revenue is recorded in a sale: cut-off, bill-and-hold, percentage of completion, deferred revenue, rebates, channel stuffing and warning signs.
- Sell-Side Quality of Earnings Report: Scope, Timing and How to Use It: What a sell-side quality of earnings report covers, when an owner should commission it, who should perform it and how to use it in the CIM and with buyers.
- Quality of Earnings Findings That Reduce Price and How to Pre-Empt Them: The quality of earnings findings that most often lower a sale price, such as rejected add-backs and cut-off errors, with how each appears and how to pre-empt it.
- Managing the Diligence Process as a Seller: Request Lists, Q&A and Response Discipline: How a seller runs due diligence: one point of contact, a request tracker, staged disclosure, a Q&A log and response discipline while the business keeps performing.
- Proof of Cash: How Buyers Test Revenue and Expenses Against the Bank: A proof of cash reconciles bank deposits and disbursements to reported revenue and expenses. See how buyers run it, what the gaps reveal and how a seller prepares.
This guide is general education. It is not a valuation opinion, appraisal, investment advice, or legal or tax advice. How these guides are made.