Foakes v Beer [1884] UKHL 1 is an English contract law case, which applied the controversial pre-existing duty rule in the context of part payments of debts. It is a leading case from the House of Lords on the legal concept of consideration. It established the rule that prevents parties from discharging an obligation by part performance, affirming Pinnel's Case (1602) 5 Co Rep 117a. In that case it was said that "payment of a lesser sum on the day [i.e., on or after the due date of a money debt] cannot be any satisfaction of the whole."

English contract law is the body of law that regulates legally binding agreements in England and Wales. With its roots in the lex mercatoria and the activism of the judiciary during the Industrial Revolution, it shares a heritage with countries across the Commonwealth, from membership in the European Union, continuing membership in Unidroit, and to a lesser extent the United States. Any agreement that is enforceable in court is a contract. A contract is a voluntary obligation, contrasting to the duty to not violate others rights in tort or unjust enrichment. English law places a high value on ensuring people have truly consented to the deals that bind them in court, so long as they comply with statutory and human rights.