Two advisors quoting the same $20m sale can be $520,000 apart.

What does a sell-side advisor actually charge?

Three components, in almost every case. A work fee paid during the engagement, a success fee paid at closing, and reimbursement of out-of-pocket expenses. The work fee is usually credited against the success fee, so it is a timing device rather than an addition: 77% of advisors deduct engagement fees from the success fee (Axial, 2026 M&A Fee Guide, 331 responses collected in Q2 2026, published 23 June 2026).

Where the market has moved is the shape of the work fee, not its existence. Firms charging a single upfront retainer fell to 26% in 2023 from 44% the year before, while monthly fees became the most common structure at 37%, and 10% of advisors adopted milestone fees payable at defined points in a process (Firmex, Global M&A Fee Guide 2023-24, based on an online survey completed by 456 middle-market professionals in December 2023). By Q2 2026, 71% of advisors charged some form of upfront fee, and nearly a third charged none at all, up from 19% in 2024 (Axial, June 2026).

The success fee is then quoted on one of three shapes. A declining scale, the Lehman formula and its variants, where the percentage falls as the price rises. A flat percentage regardless of size. Or an accelerator, where the percentage rises above an agreed target price. In the December 2023 survey the split was 51% declining, 32% flat and 17% accelerator. By Q2 2026 flat-percentage structures had risen to 36%, with declining scales and flat fees together accounting for 79% of responses (Axial, June 2026).

The classic Lehman scale is 5% of the first $1m of price, 4% of the second, 3% of the third, 2% of the fourth and 1% of everything above $4m. Double Lehman doubles each tier to 10, 8, 6, 4 and 2%, and is the version still in general use below roughly $25m to $50m of value. Both were designed in an era of much smaller deals, which is why the effective rate on a modern middle-market transaction rarely resembles either headline number.

How much is the success fee?

On the most recent published grid, the average quoted success fee ran from 5.5% on a $5m transaction to 3.7% at $20m, 2.1% at $100m and 1.7% at $150m (Firmex, Global M&A Fee Guide 2023-24, surveyed December 2023).

The average is the least interesting number in that sentence. At $20m, 80% of the quotes fell between 2.0% and 4.6%. That is a spread of 2.6 percentage points across the middle four-fifths of the market, or roughly $520,000 of fee on the same $20m sale, before anyone has argued about what is included in the price the fee is calculated on.

Dispersion that wide is not noise. Advisors say the largest single input into a success fee quote is the risk of not closing, cited as very important by 61% of respondents, ahead of engagement size at 60% and transaction complexity at 59% (Firmex, December 2023). A quote is therefore partly a statement about the business being sold. A number at the top of the range on a clean asset is a different signal from the same number on a concentrated, founder-run one.

Two definitional points move real money and are settled in the letter, not the market. First, what the percentage applies to: fees are generally calculated on enterprise value at closing including deferred consideration such as notes, escrows, holdbacks and rollover equity, with earnout fees collected as and when the earnout is paid. Second, the tail, the period after termination during which a transaction still triggers a fee, which is commonly 12 to 24 months.

What is the work fee, and is it credited?

Half the advisors surveyed put their monthly fee at $5,000 to $10,000. Firms of 50 or more people most commonly charged $10,000 to $15,000 a month, and levels above $15,000 were rare. One-time upfront retainers varied more by firm size than deal size: firms of 20 or fewer people typically charged $10,000 or less, while firms above 20 people most commonly received $25,000 or more (Firmex, December 2023).

Advisors are direct about what the fee is for. It funds the preparation work that happens before any buyer sees anything, and it tests whether the seller is committed. Firms describe it as a commitment fee more often than as compensation, and the surveyed comments repeat the point that engagement fees rarely cover the cost of a broken deal.

The number to negotiate is not the monthly figure. It is whether the fee is credited in full against the success fee, whether it stops if the process is paused, and what happens to it if the seller withdraws. Those three answers change the economics of a stalled process far more than the difference between $7,500 and $10,000 a month.

How good is this fee data?

Thinner than the confidence with which it is usually quoted, and worth saying so.

There is no regulator, exchange or professional body that publishes middle-market M&A advisory fees. Every figure above comes from a vendor survey of advisors: Firmex, a data room provider, and Axial, a deal network. Both survey the sell side about what it charges, which is self-reported pricing rather than observed engagement letters or realized fees. Neither audits the answers.

The two available surveys also answer different questions. The most current, Axial's, was fielded in Q2 2026 and published in June 2026, but reports fee structures rather than fee levels: it says how many advisors use a declining scale, not what the scale is. The last freely published grid of success fee percentages by deal size comes from Firmex's survey of December 2023. So the shape of the market is current to this year and the price of it is two and a half years old, in a period when 47% of advisors said they had raised at least one component of their fee (Firmex, December 2023) and Firmex's following North American edition reported that share falling to 30% (Firmex, North American Edition, 289 advisors in the United States, Canada and Mexico, published 1 May 2025 on 2024 data).

The widely circulated fee-band tables are older still. The most linked one dates to a September 2016 article last updated in March 2024 (Divestopedia, A Summary of M&A Fees for Sell-Side Transactions), and puts retainers on sub-$100m transactions at $50,000 to $150,000 in total with a guideline that they should not exceed 15% of combined fees. The academic literature on advisory fees is real but almost entirely concerned with large public-company transactions, which price nothing like a $20m private sale.

Treat every number in this article as a well-sourced central tendency with a wide distribution around it and a date attached, not as a rate card.

What does the fee buy?

Work that happens before a buyer exists, and tension once one does. The preparation phase produces the normalized earnings picture, the buyer universe, and the materials. The process phase produces competition, which is the only mechanism that moves a price above the first credible offer. Neither is visible in a fee schedule, which is why fee comparison across two proposals is rarely a like-for-like exercise.

The comparison that is like-for-like is structural. A declining scale pays the advisor a lower marginal rate on exactly the dollars a seller most wants fought for. An accelerator, where the percentage rises above an agreed target, inverts that. Roughly one advisor in six offers the accelerator shape, so it exists in the market and is available to ask for.

The other structural question is what the fee attaches to. If a meaningful part of the consideration is contingent, the treatment of earnout dollars in the fee schedule decides whether the advisor is paid on money the seller may never receive.