Off-market deal flow: how proprietary sourcing actually works — with the math.

“Proprietary deal flow” is the most-claimed and least-audited phrase in buy-side M&A. Every firm says it; almost none will show the machine. Here is what off-market sourcing actually involves — what qualifies, what it costs to run, and the arithmetic that separates an engine from a mailing list.

What counts as off-market — and what is mislabeled

An off-market deal has one defining property: the first conversation happened because the buyer’s side started it. The owner had not listed, had not engaged a broker, and was not running a process. Approached directly and by name, qualified against a written buy box, introduced to one acquirer. That is the whole definition — and most of what wears the label fails it. A CIM forwarded “before it goes wide” is not off-market; it is early access to an auction. A database export of companies “likely to sell” is not deal flow; nobody has spoken to an owner. A listing shared from a “private network” is a listing. The test is simple: if a process existed before you arrived, it is not proprietary. The full comparison sits in off-market vs. brokered deals.

The auction tax, quantified

The economic case for off-market flow is two numbers wide. First, the embedded fee: a brokered target carries the seller’s 6–10% commission inside its price — on a $6M deal, $360,000 to $600,000 the buyer pays before negotiating anything. Second, the bidding: a listed process is designed to show the same asset to every buyer in the market, and the winner is the one who paid the most. Off-market, both terms drop out. There is no listing fee in the price because there is no listing, and there is no premium from competing bidders because there are none — the table has one buyer at it. The negotiation becomes what it should have been all along: a conversation about fit, structure, and the owner’s next chapter.

Off-market is not a discount strategy. It is a fit strategy — the whole market considered, not whatever happens to be listed.

The cadence math: from 1,000 reaches to a closing

What the label “proprietary” hides is that off-market sourcing is a volume discipline. Most owners are not for sale at any given moment — the funnel only becomes predictable when the top of it is industrial. Sentinel’s operation runs at roughly a thousand owner reaches a day; since 2020 that has compounded into more than a million owner outreaches and 5,000+ qualified calls arranged. At mandate level, the working arithmetic looks like this:

Sentinel operating figures. Across the practice since 2020: 100+ closings from $800K to $96M, with $500M+ deployed alongside partners.

Two implications follow from the math. Ratios like these are why a two-analyst corp-dev team cannot brute-force proprietary flow next to its day job — the top of the funnel starves first, quietly. And volume is why the pipeline stays full continuously rather than in bursts: at a thousand reaches a day, the funnel stops being a sequence of lucky finds and becomes a rate. What that produces at each checkpoint of a first quarter is set out in the day-30/60/90 pipeline benchmarks.

Why 95%+ of it never hits a broker’s site

Across Sentinel’s mandates, more than 95% of introduced targets never appear on any listing platform — and the reason is structural, not clever. The owners best worth acquiring are the least likely to list: their businesses run well, nothing forces a sale, and brokers find them exactly as hard to reach as buyers do. They transact when a credible, specific acquirer arrives before a process exists. Reaching them first is the entire game — and it is won at the top of the funnel, by coverage, not at the bottom by negotiation. That is also why genuinely proprietary targets are introduced to one acquirer: shown to three buyers, an off-market deal becomes a private auction, and every advantage above evaporates.

Can you run this in-house?

Yes — platforms do, and the honest accounting is worth writing down before choosing. Running the cadence internally means dedicated outreach staffing (the volume is a full-time production job, not a side task for analysts), data and tooling for universe mapping, a qualification layer senior enough to hold a credible owner conversation, and a manager who keeps the machine at rate through the months when nothing closes. Most platforms that build it well are past eight or ten acquisitions a year, where the fixed cost amortizes. Below that, the arithmetic tends to favor renting the engine and keeping the internal team on strategy, approvals, and execution — the parts that cannot be delegated. The wrong answer is the common one: assigning proprietary sourcing to two analysts as a fourth priority, then concluding after a year that off-market flow does not work.

How to audit any firm’s “proprietary” claim

The claim is free; the machine is not. Five questions expose which one you are buying:

• Outreach volume, in writing. How many owners do you reach per day, and how? An engine states its cadence; a database vendor changes the subject.
• The 95% test. What share of your last fifty introductions ever appeared on a listing platform? High single digits or better is an engine.
• The qualification standard. Show me the written definition of a qualified call. If it is not in the agreement, every meeting will count.
• The exclusivity rule. Is any target ever shown to more than one buyer? The only acceptable answer is no — one target, one partner.
• The funnel, stage by stage. Reaches, conversations, qualified calls, and introductions from a recent 90-day window. Real operations have these numbers on hand; verified closings sit on the results page.

Notice what is absent from the list: adjectives. Every question above resolves to a number, a document, or a yes/no — which is the point. The claim “proprietary deal flow” cannot be audited; a stated daily cadence, a written qualification standard, and a stage-by-stage funnel can. Any firm that clears all five is running the real thing. That machine — mapped, staffed, and reported weekly against a written floor — is exactly what the buy-side deal sourcing retainer retains.

Off-market questions, answered directly

What does off-market mean in M&A?

An off-market (or proprietary) deal is one sourced by approaching an owner directly — by name, before any listing, broker, or auction exists. The owner was not for sale yesterday; the first conversation happens because the acquirer’s side started it. More than 95% of the targets Sentinel introduces never appear on a broker’s site.

Why are off-market acquisitions cheaper in total?

Two costs disappear. The seller’s brokerage fee — commonly 6–10% of price — is not embedded in what the buyer pays, and there is no auction bidding the multiple up. On a $6M transaction the embedded fee alone is $360,000–$600,000, before the bidding premium; the off-market route replaces both with one quiet negotiation on fit.

How much outreach does real off-market deal flow require?

More than most acquirers expect, because most owners are not for sale at any given moment. Sentinel’s operation runs roughly a thousand owner reaches a day — over a million outreaches since 2020 — to sustain 3–5 qualified calls a week on an active mandate. Any firm claiming steady proprietary flow without stating its outreach volume is describing a database, not an engine.

How can I verify a firm’s “proprietary deal flow” claim?

Ask five things: outreach volume per day in writing; what percentage of introductions never appeared on any listing platform; the written definition of a qualified call; whether any target is ever shown to more than one buyer; and stage-by-stage funnel numbers from a recent 90-day period. A firm with a real engine answers all five without hesitation.