How a retainer works
A retainer is a fixed amount paid monthly, or occasionally as a single upfront fee, for the duration of the mandate. It compensates the advisor for committed capacity regardless of outcome.
For the company, the cost is known and spread over the process. For the advisor, it covers the substantial work performed before any transaction is certain: preparation, materials, target list construction and early outreach.
Retainers also serve a filtering function. Advisors use them to confirm that a client is committed, since processes abandoned after two months are costly for a firm working on pure contingency.
How a success fee works
A success fee is a percentage of transaction value payable when the transaction completes. Percentage rates decline as transaction size rises, and most mandates include a minimum fee.
The attraction for founders is obvious: no completion, no fee. The trade-off is that the advisor is pricing the risk of failure into the percentage, so the completed-deal cost is higher than it would be under a paid-capacity model.
The detail that matters is the fee base. Whether debt, cash, earn-out payments and rollover equity count toward transaction value can change the amount owed substantially.
What each structure incentivises
A pure success fee rewards completing something. That is aligned when your objective is to complete, and less aligned when the better decision might be to wait two quarters, reject a weak offer or stop the process entirely.
A pure retainer removes that pressure but also removes the financial incentive to push for the last increment of value, and it places all the risk of a failed process on the company.
The hybrid exists because both distortions are real. A modest retainer covers committed capacity, and a success fee, ideally with a higher rate above a target level, aligns the advisor with the outcome.
Common hybrid structures
Retainer credited against success fee. Monthly payments are deducted from the success fee at closing, so the retainer functions as an advance rather than an additional cost.
Tiered success fee. A base percentage up to a target valuation, then a higher percentage on value above it. This is the most direct way to align the advisor with price maximisation.
Capped retainer. Monthly payments stop after an agreed number of months, protecting the company if the process runs long.
Milestone payments. A portion payable at defined stages such as materials completion or receipt of first indicative offers, useful when the process is expected to be lengthy.
The clauses that determine your real cost
Definition of transaction value. The single most important term.
Trigger point. Payable on signing or on receipt of funds, and how deferred consideration is treated.
Minimum fee. Applies regardless of the percentage calculation.
Tail period. How long after termination a fee remains payable on transactions with introduced parties, and how introduction is defined. Six to twelve months is common; longer periods deserve scrutiny.
Exclusivity. Whether you may run parallel conversations directly and whether a fee is due if you close with a party you introduced yourself.
Expenses. Capped or uncapped, and what requires approval.
Termination. Notice period and amounts owed on exit.
Choosing a structure for your situation
If the transaction is well defined and likely to complete, weight the structure toward success fee and negotiate a tier above your target.
If the process is exploratory or the outcome uncertain, expect the advisor to require a meaningful retainer, and consider whether a narrower fixed-fee engagement would serve you better than a full mandate.
If cash is tight, a credited retainer keeps monthly cost lower without asking the advisor to work entirely at risk.
Whatever structure you agree, have transaction counsel review the engagement letter. This article describes how these arrangements are commonly structured and is not legal or financial advice.