Diligence is good at the things that hold still. Contracts, receivables, customer concentration, the quality of earnings, the working capital peg. Those get checked properly because they can be checked properly — the evidence exists in a file somewhere and either supports the number or does not.
In a services business, none of that is where the risk lives. The asset walks out of the building at five o'clock and decides overnight whether to come back.
Whose relationship is it, actually
The contract names the company. Ask the client who they work with and they name a person.
That gap is the single most expensive thing a buyer can misread, and it does not appear in any schedule. A services business with ten clients and one relationship owner does not have ten client relationships. It has one, held by someone who may or may not stay, and who has just watched the owner get paid.
The check is not complicated and almost nobody runs it. In the client reference calls, do not ask whether they are happy. Ask who they would call first if something went wrong tomorrow.
Whether the process exists or just happens
Every services business claims a process. Some have one. Most have a person who has done the work long enough that the sequence lives in their head, and a document written for a previous owner that describes a version of it from four years ago.
The difference matters at exactly one moment: when that person is not there. Which is a moment the buyer, not the seller, will be present for.
Ask to see the last three pieces of work delivered and the steps that produced each. If the answer is a description rather than a record, the process is a person.
What the owner does that nobody has priced
The add-back schedule adjusts the owner's salary to a market rate for a general manager. Fine, as far as it goes.
It rarely goes far enough. The owner who is also the head of sales, the final quality check, and the one who takes the difficult client call is not one hire at market rate. That is three roles, and two of them are hard to fill in a business that has just changed hands.
The number to build is not what the owner is paid. It is what it would cost to replace everything the owner does, at market, hired by a stranger.
The bench nobody looks at
Diligence looks at the org chart, which shows who reports to the owner. The useful question is different: who could do the owner's job in eighteen months, and do they know it.
A services business with a real second tier survives a transition. One without a second tier is a business where every ambitious person already left, and the reason they left is usually still in place.
The test
Ask what breaks in the first week if the three most senior people are gone.
If the answer is a manageable list, you are buying a business. If the answer is everything, you are buying a payroll and a client list, and the price should reflect the difference.