How do add-ons work in football transfers?

What the report says

BBC Sport Football’s Ask Me Anything team explained how transfer “add-ons” work, using several current and past deals to show why reported fees in football can be misleading. The article, published on 13 June 2025, noted that many summer transfers are announced with a base price plus possible extra payments, such as Chelsea’s move for Rayo Vallecano defender Pep Chavarria and Brighton’s signing of Charalampos Kostoulas.

The piece said add-ons are usually tied to performance conditions and are often kept private. They can be relatively straightforward, such as appearance milestones or goals, or more ambitious, including team achievements like qualifying for Europe or winning major honours. BBC Sport also pointed to cases where the exact trigger for an add-on has been disputed or unclear, underlining how difficult it can be to judge a deal’s true cost from public reports alone.

The article added that these clauses can materially affect club accounts. It cited Manchester United’s latest financial results, which recorded a potential liability of £138.82m linked to transfer-related add-ons and other contingent payments, including sums tied to appearances, team success, contracts and awards. The examples of Anthony Martial, Mason Mount and Darwin Nunez were used to illustrate how such clauses can range from highly achievable to extremely difficult.

More broadly, the article explained that add-ons are meant to balance risk between buying and selling clubs: the seller can benefit if a player thrives, while the buyer may pay more only if certain conditions are met.