noun
contract money; down payment
Money paid at the time of signing a contract, often as a deposit or initial payment. Common in real estate, entertainment, and sports contracts.
新しいアパートを借りるとき、契約金として家賃の2ヶ月分を払った。
When renting a new apartment, I paid two months' rent as contract money.
プロ野球選手の契約金は年々高くなっている。
The signing bonuses for professional baseball players are increasing year by year.
頭金 is a down payment on a large purchase like a house or car, typically a percentage of the total price, whereas 契約金 is the money paid at contract signing, which may include various fees.
Compound of 契約 (contract) and 金 (money).