The dealing spread, also known as the bid-ask spread, is the difference between the highest price a buyer is willing to pay (bid) and the lowest price a seller is willing to accept (ask) for a security. This spread represents the cost of immediate liquidity and is a primary source of revenue for market makers and dealers who facilitate trading.

Dealing spreads vary based on liquidity, volatility, and market conditions. Highly liquid instruments like major currency pairs typically have tight spreads (1-3 pips), while less liquid assets may have wider spreads. Traders must consider dealing spreads when calculating potential profits, as positions must move beyond the spread to become profitable.

Real-world example: EUR/USD shows a bid of 1.1050 and ask of 1.1052, creating a 2-pip dealing spread that traders must overcome before achieving profitability on new positions.