A retainer is a recurring fee (typically monthly) paid to a corporate advisor during a sell-side mandate, in addition to the success fee at close. Australian sub-$20M sell-side mandates typically charge $10,000 to $30,000 per month, with the negotiation point being whether the retainer is creditable against the success fee at completion (every retainer dollar reducing the success fee by a corresponding amount) or non-creditable (paid on top of the success fee).
Whether the retainer is creditable is the single most consequential negotiation point in this fee category, often worth $100,000 or more across a nine-month process. Sellers should push for full creditability; if the advisor refuses, treat the retainer as a separate and additional cost.