Access Rule (Rule 610)
Market Microstructure glossary · Limit Order Book Mechanics & Order Routing Logic
Definition
The Regulation NMS rule capping the fees that venues may charge for accessing protected quotes and requiring fair and non-discriminatory access.
Access Rule (Rule 610) in plain English
Think of the stock market as many different 'shops' (called venues) all selling the same stock, and the law wants your order to reach whichever shop has the best price. Rule 610 is a fairness referee: it caps how much a venue can charge just to trade against its best posted price (roughly $0.003 per share, three-tenths of a cent), and it forbids letting some traders in while shutting others out. The point is that a great-looking price isn't secretly eaten up by fees or blocked by unfair access. In short, it keeps the 'best price' actually reachable by everyone on equal terms.
Also called: Rule 610
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