In the standard Monopoly board game, the smallest banknote is the $1 bill.
The classic American set uses denominations of $1, $5, $10, $20, $50, $100, and $500. The $1 note is useful for settling small differences, including certain rents and charges, although many payments during a game involve larger denominations.
Monopoly money is fictional currency rather than legal tender. Its colorful bills are designed for gameplay and have no value outside the game. The bank holds the money, property deeds, houses, and hotels that have not yet been distributed to players.
Regional editions may print equivalent values in another currency or use different artwork. The $1 answer refers to the classic United States-style edition. Players sometimes assume the $5 note is the smallest because it appears more frequently in casual play, but the standard bank includes $1 bills.