Money earned by a player for signing his contract. Typically paid out within the first 12-18 months. Prorated against the salary cap for the life of the contract (five-season maximum). This is how the Lions could afford to give Matthew Stafford a $50 million signing bonus in 2017. For cap purposes, Stafford’s signing bonus counts for $10 million against the Lions‘ salary cap for each of the first five seasons of his contract.
Largest signing bonus in a contract: Russell Wilson, $65 million with the Seahawks. Wilson had one year left on his contract when he signed a 4-year extension (5 seasons total), and his signing bonus will count $13 million against the salary cap.