Customer Concentration Risk Assessment: Free Scoring Framework for Australian Business Buyers

Customer concentration risk is one of the most common ways business buyers in Australia lose money quietly. You buy a business that looks profitable, the handover goes smoothly, and then three months later your largest client takes their work elsewhere — and suddenly a third of your revenue is gone without warning.

The problem is that "customer concentration risk" sounds abstract until it isn't. Most sellers don't volunteer it. Most buyers don't know exactly what to measure. And most brokers will tell you the revenue is "diversified" if the top client is only 40% of the total (which, for the record, is not diversified).

This assessment framework gives you a scoring system to evaluate concentration risk before you sign anything. It works across all Australian trades and services businesses — cleaning, pest control, HVAC, plumbing, electrical, landscaping, and similar.

What is customer concentration risk?

Customer concentration risk is the degree to which a business depends on a small number of customers for a large portion of its revenue. In Australian SME acquisition finance, most lenders want to see no single customer exceeding 20–25% of total revenue. Beyond that threshold, they treat the revenue as structurally fragile — and they're right to.

The risk compounds when the concentration is paired with weak contracts or owner-dependent relationships. A plumbing business doing 35% of revenue with one large strata management company is genuinely risky if that relationship is a verbal handshake with the previous owner (which is more common than it should be).

I saw a deal last year where a cleaning business had three major commercial clients — council facilities, a shopping centre, and a hotel group — making up 78% of revenue. The seller called this "blue chip." The buyer called it "diversified." What it actually was: three contract renewal conversations away from a crisis.

Why this matters more than the headline EBITDA

Due diligence on financials tells you what happened in the past. This assessment tells you whether that revenue is likely to survive the ownership change. These are different questions, and you need answers to both.

If you haven't already, read the full guide on customer concentration risk when buying a business — it covers the mechanics and red flags in detail. The assessment below gives you a structured scoring tool to go alongside it.

For the broader due diligence picture, the Due Diligence Checklist and Financial Red Flags Checklist cover the territory this framework doesn't.

This is Module 5 of the Playbook — confirmatory due diligence.

What the framework covers

The full assessment below scores your target business across four dimensions:

Revenue concentration — how much of total revenue is tied to the top 1, 3, and 5 customers
Contract security — whether those relationships are written, contractual, and transferable
Relationship dependency — whether the concentration is tied to the owner personally
Diversification buffer — whether the long tail of smaller customers could absorb a loss

Each dimension produces a score. Your total score maps to a risk rating with a recommended action: proceed, negotiate, or walk.

Customer Concentration Risk Assessment Framework

How to use this framework: Score each item honestly using the provided scale. Add up each section subtotal, then total all sections for your final risk rating. Be conservative — when in doubt, score the worse option.

Section 1: Revenue Concentration

Score each item. Use trailing 12-month revenue figures from the verified financials.

Metric	Score	Your Score
Top 1 customer = under 10% of revenue	0
Top 1 customer = 10–20% of revenue	2
Top 1 customer = 20–35% of revenue	5
Top 1 customer = over 35% of revenue	10

Metric	Score	Your Score
Top 3 customers = under 25% of revenue	0
Top 3 customers = 25–40% of revenue	2
Top 3 customers = 40–60% of revenue	5
Top 3 customers = over 60% of revenue	10

Metric	Score	Your Score
Top 5 customers = under 40% of revenue	0
Top 5 customers = 40–60% of revenue	2
Top 5 customers = 60–80% of revenue	5
Top 5 customers = over 80% of revenue	10

Section 1 subtotal (max 30): ____

Section 2: Contract Security

Assess the nature of the relationship with your top 3 clients by revenue.

For each of your top 3 clients, score the contract type:

Contract Type	Score per Client
Signed multi-year contract with termination clause	0
Signed annual agreement, auto-renewing	1
Signed agreement, month-to-month	3
No written contract — verbal/ongoing arrangement	6

Add the score for each of your top 3 clients.

Client 1 contract score: ____ Client 2 contract score: ____ Client 3 contract score: ____

For each of your top 3 clients, score the transferability:

Transferability	Score per Client
Contract reviewed — no change-of-control clause	0
Contract not yet reviewed for change-of-control	2
Change-of-control clause exists — consent required	4
Change-of-control clause exists — client can terminate	8

Add the score for each of your top 3 clients.

Client 1 transferability score: ____ Client 2 transferability score: ____ Client 3 transferability score: ____

Section 2 subtotal (max 42): ____

Section 3: Relationship Dependency

This section assesses whether the concentration is tied to the owner personally. See the Owner Dependency Scorecard for a deeper dive on this dimension.

Question	Yes = points	No = 0
Does the top client relationship exist primarily due to the owner's personal relationship?	8	0
Has the owner personally introduced you to the top client before/during the sale?	0 (positive sign)	2 (red flag — hasn't happened)
Would the top client likely tender or review their arrangement following a change of ownership?	7	0
Is the day-to-day contact at the top client organisation the owner themselves?	6	0
Has the top client been with the business for less than 3 years?	3	0
Has revenue from the top client grown significantly in the last 12 months?	2	0

Section 3 subtotal (max 28, noting one negative): ____

Section 4: Diversification Buffer

Assess the depth and resilience of the customer base beyond the top clients.

Metric	Score	Your Score
50+ active customers in trailing 12 months	0
20–49 active customers	2
10–19 active customers	5
Under 10 active customers	10

Metric	Score	Your Score
Long tail (customers ranked 6–20) = over 30% of revenue	0
Long tail = 15–30% of revenue	2
Long tail = 5–15% of revenue	4
Long tail = under 5% of revenue (essentially no tail)	8

Metric	Score	Your Score
Revenue from 3+ distinct industries/sectors	0
Revenue from 2 industries/sectors	2
Revenue from 1 industry/sector only	5

Section 4 subtotal (max 23): ____

Total Score and Risk Rating

Add all four section subtotals:

Total Score: ____ / 123

Total Score	Risk Rating	Recommended Action
0–15	Low	Proceed. Concentration risk is manageable.
16–30	Moderate	Proceed with conditions. Consider price adjustment or specific warranty clauses.
31–50	High	Negotiate hard. Require retention protections, deferred consideration, or price reduction.
51–75	Very High	Seek major concessions or walk. The risk profile doesn't justify a standard multiple.
76+	Extreme	Walk unless there is an extraordinary compensating factor.

Scoring Interpretation Notes

Score 0–15 (Low Risk) The revenue base is genuinely diversified, contracts are solid, and the key relationships aren't dependent on the exiting owner. This is the profile you want. Most banks will finance this without requiring haircuts on the revenue.

Score 16–30 (Moderate Risk) Some concentration exists but it's manageable with the right protections. Ensure the SPA includes appropriate warranties about customer relationships, and consider whether an earn-out on the top client revenue makes sense. Check whether the contracts have been reviewed for change-of-control provisions before settling.

Score 31–50 (High Risk) You're taking on genuine concentration risk. Before proceeding, you need: (a) written confirmation from the top clients that they'll continue post-sale, (b) either a price reduction or a deferred/contingent payment structure that absorbs the downside, and (c) a clear plan for diversifying the customer base in your first 90 days.

Score 51–75 (Very High Risk) The revenue is structurally fragile. Even a well-priced deal can go south quickly if one or two large clients walk. If you proceed, the deferred consideration should represent a significant portion of the purchase price — enough that the seller shares meaningfully in the downside if customers don't stay. Get independent legal and financial advice before committing.

Score 76+ (Extreme Risk) The business depends on so few clients with so few protections that even a small churn event could threaten viability. This is not a price negotiation — this is a fundamental structural problem with the business. Extraordinary circumstances aside (e.g., you have a personal relationship with the key clients that transcends the business), this is a walk.

What to Do With Your Score

Before you sign the LOI: Run this assessment on the information-memorandum data. If you're already at High or Very High, flag it early — before you spend money on formal due diligence.

During confirmatory due diligence: Verify every input. Get contract copies. Check change-of-control clauses. Ring the clients. Cross-reference invoices against the bank statements. See checking the financials during due diligence for the verification process.

In the SPA: If your score is Moderate or above, make sure the SPA includes:

A warranty that no major customer has indicated they will cease trading post-settlement
A material adverse change clause that covers loss of a named major customer before settlement
Where possible, a deferred/earn-out component tied to the top client/s retaining their revenue for 6–12 months post-settlement

For due diligence on a small business more broadly, combine this framework with the owner dependency assessment — the two risks often travel together.

This framework is a guide, not financial advice. For significant acquisitions, work with a qualified accountant and commercial solicitor who can review the specific contracts and structure appropriate protections.

Customer Concentration Risk Assessment: Free Scoring Framework for Australian Business Buyers

What is customer concentration risk?

Why this matters more than the headline EBITDA

What the framework covers

Get the free scoring framework