Under the price-time priority principle, which rule is true when two orders share the same limit?

Under the price-time priority principle, which rule is true when two orders share the same limit?

• A. Unlimited orders have highest priority for matching
• B. The order with a better price is executed first
• C. The oldest order is always executed first
• D. For orders with the same limit, the order first received is executed first

Answer: (D)

Price-time priority pairs two ideas: fill at the best price first, and if prices are the same, break ties by which order arrived first. When two orders share the same limit, there is no price difference to favor one over the other, so the winner is the one that was placed earliest. This keeps the market fair and predictable for traders who set the same price. The idea of unlimited orders doesn’t fit the matching rules, and if there were a better price, that would take precedence, but that isn’t the situation here. Saying the oldest order is filled first aligns with the same time-priority concept—the earliest received order gets executed before later ones.

Price-time priority pairs two ideas: fill at the best price first, and if prices are the same, break ties by which order arrived first. When two orders share the same limit, there is no price difference to favor one over the other, so the winner is the one that was placed earliest. This keeps the market fair and predictable for traders who set the same price. The idea of unlimited orders doesn’t fit the matching rules, and if there were a better price, that would take precedence, but that isn’t the situation here. Saying the oldest order is filled first aligns with the same time-priority concept—the earliest received order gets executed before later ones.