The Client Concentration Problem That Kills Deals at the Finish Line

Accounting firm client concentration risk is one of the quietest deal-killers in practice sales. A single client above 10% of revenue typically triggers a discount, and above 20% it’s what buyers call a walk-away number. The frustrating part is most sellers don’t find out how exposed they are until due diligence is already underway, months into a process they assumed was nearly done.

We’ve watched deals fall apart in the final stretch more than once, and it’s rarely because the seller lied about anything or the numbers were wrong. It’s because nobody flagged the concentration problem early enough for the seller to actually do something about it.

Single-client concentration above 10% of revenue is a discount trigger, and above 20% it’s often a deal-killer entirely. That’s not a soft guideline buyers occasionally apply. It’s close to a hard line for a lot of institutional and even individual buyers.

At New Clients, Inc., accounting firm client concentration risk is one of the first things we walk sellers through before a firm ever goes to market, precisely because finding it during due diligence is far too late to fix it gracefully.

What exactly is client concentration risk in an accounting practice sale?

It’s the risk a buyer takes on when a meaningful share of a firm’s revenue depends on just one or a handful of clients. If that client leaves after the sale, for any reason- a relationship change, a competitor pitch, simple dissatisfaction with new ownership- the buyer’s return on the deal takes a direct hit. The more revenue tied to fewer clients, the more the entire purchase price rests on relationships the buyer doesn’t actually control yet.

Buyers aren’t being paranoid when they flag this. They’re pricing in a real, specific risk. A firm that looks financially strong on paper can be quietly fragile if that strength traces back to two or three long-tenured clients rather than a broad base.

At what percentage does client concentration actually start hurting a deal?

A single client representing more than 10% of revenue is generally where the discount starts showing up in the multiple, and above 20% concentration in one client is often where buyers walk entirely. Some buyers apply a similar lens to the top three or five clients combined, not just the single largest one, so a firm can technically have no single client over 10% and still carry real concentration risk if its top five clients together represent an outsized share of revenue. 

Here’s roughly how that risk tends to translate into deal terms:

None of these numbers are arbitrary. They reflect how much of the deal’s future performance is riding on relationships the buyer is inheriting rather than building.

Why does client concentration surface during due diligence instead of earlier in the process?

Because most sellers never break their revenue down by client until a buyer’s team specifically asks for it. A firm owner knows their biggest clients by name, obviously, but rarely sits down and calculates exactly what percentage of total revenue any single relationship represents until diligence forces the exercise.

By the time that math gets done, usually weeks or months into a live deal, the seller has already invested real time and emotional energy into the sale. Discovering a concentration problem at that stage doesn’t just risk the price. It risks the entire transaction falling apart after the seller has told staff, sometimes told key clients, and mentally checked out of day-to-day ownership.

Can client concentration risk be fixed before a firm goes to market?

Yes, but it takes real lead time, not a quick fix in the weeks before listing. Firms that spend 12 to 18 months actively managing concentration, growing other client relationships faster or intentionally working to reduce dependence on the dominant client, tend to preserve their multiple rather than taking the hit at the negotiating table.

The fix isn’t firing a large client, that would be its own kind of self-inflicted damage. It’s deliberately growing the rest of the client base so that same large client, even if its revenue stays flat, becomes a smaller percentage of a bigger, more diversified total. 

If concentration can’t be fixed in time, does that mean the firm just can’t be sold?

Not at all. It means the deal gets structured differently rather than falling apart entirely. Buyers facing real concentration risk often still move forward, just with heavier retention holdbacks, a larger earnout tied specifically to that key client staying on, or a lower upfront cash percentage with more of the price deferred and contingent on the relationship surviving the transition.

That’s a worse outcome for a seller than avoiding the discount altogether, but it’s a much better outcome than having the deal collapse at the finish line because concentration got discovered too late to structure around intelligently. Knowing the number early is what turns a potential dealbreaker into a manageable negotiation point instead.

FAQs

What percentage of revenue from one client is considered a red flag in accounting firm sales?

A single client above 10% of total revenue triggers a valuation discount, and above 20% is treated as a deal-killer by buyers, particularly institutional and PE-backed buyers evaluating the firm.

Why does client concentration risk get discovered so late in the sale process?

Most sellers never calculate their exact revenue-by-client breakdown until a buyer’s due diligence team specifically requests it, which means the risk surfaces months into a deal rather than before the firm goes to market.

Can a firm reduce its client concentration risk before selling?

Yes, though it takes real time. Firms that spend 12 to 18 months actively growing their other client relationships, rather than trying to shed the concentrated client, tend to preserve their valuation multiple more effectively.

Does concentration risk only apply to a single client, or does it include the top few combined?

Buyers often look at both. Even if no single client exceeds 10%, a firm where the top three to five clients together represent a large share of revenue can still face the same scrutiny and discount.

If a firm has high client concentration, does that mean it can’t be sold?

No. Deals with concentration risk still close, but with adjusted terms, larger retention holdbacks, earnouts tied to the key client staying on, or more of the price deferred rather than paid in cash at closing.