Most literary agents take 15 percent of whatever an author earns on a domestic book deal, and 20 percent when a foreign co-agent handles translation rights, a split the Authors Guild describes as generally standard and non-negotiable across the industry, calculated on the full gross amount payable to the author before any other deduction.
That structure sounds simple, but the mechanics of where the percentage lands matter more than the number itself. Because commission is taken from gross rather than net, an author's agent is paid before the author sees a dollar; the publisher issues payment to the agency, the agency deducts its cut, and the balance is forwarded to the writer, typically inside an accounting cycle the agency controls. On a foreign deal, that chain gets a second link: a sub-agent in the target market takes a slice first, and the agency's 20 percent already accounts for splitting that fee, rather than stacking on top of it.
The Association of American Literary Agents, the trade body most working agents belong to and the successor to the old AAR, does not publish a mandated commission rate in its Canon of Ethics; commission remains a private negotiation between agent and client. What the Canon does fix is the conduct around that money. Members may not charge any reading fees for evaluating work for possible representation, and must deposit funds received on behalf of clients promptly upon receipt and pay authors promptly in turn. Publishers Weekly reported on the group's most recent ethics revision, which widened membership eligibility beyond agents who had personally closed a minimum number of book deals, an acknowledgment, the organization said, that agenting alone often is not enough to sustain a career, and a signal that the profession's self-policing keeps shifting as the business does.
For a writer weighing an offer of representation, the number on the agency agreement is the easy part to check. The harder part is the exit clauses: how many months an agency can shop a manuscript before a writer can walk, and whether the agency keeps commission on deals substantially negotiated before a split. The Authors Guild's model guidance suggests limiting any post-termination claim to deals concluded within six months of leaving. Before signing, a writer should read past the percentage to the paragraph that explains what happens if the relationship ends.
For a related writing perspective, read How a Book Advance Actually Gets Paid Out.