How Does ‘Time Priority’ in Order Matching Affect the Likelihood of Positive Slippage?

Time priority is a rule where, among orders at the same price, the order that was placed earlier gets executed first. For a limit order, if the market price moves favorably, the order will be filled at the limit price (zero slippage) or better (positive slippage).

The time priority rule ensures that the limit order is executed before newer orders at the same price, increasing the chance that the favorable price is captured, potentially leading to positive slippage.