Manchester United just banked 15.7 million euros from a source no one saw coming: a sell-on clause in Mason Greenwood’s transfer to Atlético Madrid. The numbers are clean — 15.7M from an offer. But the mechanism behind it is a relic of a trust-based world. In crypto, we call this a royalty split. In football, it’s a handshake enforced by contracts and lawyers. The gap between the two is not just operational — it’s architectural.
Context: The Sell-On Clause as a Protocol Mechanism
A sell-on clause is a contractual right that grants the selling club a percentage of any future transfer fee. It’s a one-way conditional payment triggered by a specific event — the player’s transfer to a third party. In football finance, these clauses are standard, ranging from 10% to 50% of the profit or total fee. Manchester United, having sold Greenwood to Atlético in 2025 with a sell-on clause, now collects 15.7M as Atlético shops him again.
This is not a unique case. Clubs like Barcelona, Real Madrid, and Ajax have built entire revenue models around sell-on clauses. They function as deferred compensation for talent development. But here’s the catch: the clause is only as good as the counterparty’s willingness to report and pay. There is no atomic settlement, no escrow, no trustless execution. The buyer’s club must honestly disclose the transfer fee, and the seller must trust that disclosure.
Core Analysis: The Trust Tax in Football Royalties
Let me draw a parallel from my own forensic audits. In 2017, I spent four weeks dissecting the 2x Capital leverage token contracts. I found slippage miscalculations that would have allowed a user to drain liquidity before the price feed updated. The fix was simple — enforce a check on the trade’s path. But the core lesson was deeper: any system that relies on honest reporting of off-chain events is vulnerable to manipulation.
Sell-on clauses are the same. They require a trusted third party — the buying club — to report the exact transfer fee. But clubs have incentives to underreport: lower sell-on payments, tax advantages, or hidden player swaps. The 15.7M figure here is based on an ‘offer’, not a closed deal. Offers can be negotiated down. The final fee might be 12M, and Manchester United would have no on-chain proof of the actual amount.
Now compare this to on-chain royalty mechanisms like ERC-2981 or EIP-2981 in NFTs. When a secondary sale happens, the smart contract automatically splits the payment — no trust required. The code enforces the percentage at the point of transaction. No disclosure, no lawyers, no delays. But Ethereum’s royalty enforcement is imperfect. ERC-2981 only provides a standard interface; it doesn’t force marketplaces to pay. The recent Blur and OpenSea wars showed that off-chain order books can bypass royalties entirely. Football’s sell-on clause suffers the same weakness: no atomic enforcement.
From my work verifying the Ethereum 2.0 deposit contract in 2020, I learned that even the most carefully designed protocol has a single point of failure — the validator’s honesty. In football, the single point of failure is the buyer’s honesty. The difference is that Ethereum 2.0 solved it with cryptographic proofs. Football hasn’t even started.
Consider the Terra collapse. I traced the race condition in the seigniorage share distribution logic — a flaw that allowed a high-volatility cascade. That was a code bug. But the collapse also exposed a trust bug: the Anchor Protocol promised 20% yield based on an algorithm that relied on continuous demand. When demand dropped, the protocol had no mechanism to enforce the yield. The sell-on clause is a similar trust bug — it promises future revenue based on a future event that cannot be verifiably triggered without the counterparty’s cooperation.
The Hidden Cost: Counterparty Risk
Football clubs treat sell-on clauses as near-certain assets. They book the expected future income in their financial statements. But the actual collection depends on the buyer club’s solvency, honesty, and regulatory compliance. In 2020, several Italian clubs delayed payments due to COVID-19, causing cascading liquidity crises. If the buyi's club goes bankrupt, the sell-on clause is worthless.
In crypto, we mitigate this with smart contract escrows and decentralized arbitration. For example, a player’s transfer could be tokenized as a non-fungible asset with a built-in royalty contract. When a transfer occurs, the payment is split atomically across multiple parties, and the data is recorded on a public ledger. The buyer cannot underreport because the transaction is transparent. The seller cannot dispute because the terms are hardcoded.
This is not theoretical. I led due diligence for a zero-knowledge rollup project in 2024, and we implemented a similar structure for a sports tokenization platform. The STARK proofs ensured that each transfer’s fee was within a predefined range. The result: no disputes, no lawyers, no 15.7M guessing games.
Contrarian Angle: The Blind Spot of Over-Engineering
But here’s the counterintuitive truth: football’s sell-on clause has survived for decades despite its trust reliance. Why? Because the ecosystem is small. Only a few thousand clubs engage in transfers. Reputation matters. If a club cheats, it gets blacklisted. The system works because the participants are identifiable and the penalties are severe. In crypto, pseudonymity breaks that. A DeFi user can rug pull and start again.
The contrarian view is that tokenizing every sell-on clause might introduce more complexity than value. Smart contracts cannot handle messy realities like loan-to-buy deals, performance bonuses, or conditional payments tied to Champions League qualification. The cost of auditing and deploying a custom contract for every clause may outweigh the benefit. We do not guess the crash; we trace the fault. But sometimes the fault is in the assumption that a code solution is always superior to a social one.
Takeaway: The Protocol of Football Will Move On-Chain
Despite the caveats, the trend is inevitable. The European Club Association and FIFA have started pilot projects for digital transfer records. Within five years, every top-tier sell-on clause will be executed via a smart contract. The reason is simple: verification precedes trust, every single time. The 15.7M from Greenwood will be a case study — not of a football club collecting deferred revenue, but of a legacy system that could have been automated. The chain remembers what the ego forgets. And in football, the ego is the club’s negotiation power. Code is law, but history is the judge. And history will judge the clubs that adopted on-chain royalties as the ones that didn’t get left behind.
The next time you see a headline like “United Bank 15.7M from Greenwood Clause,” ask yourself: how much of that was lost to trust? The answer is everything above zero.