The National Association of Securities Dealers has identified five fields in its trade reporting requirements to identify exceptions to Regulation NMS Rule 611’s requirements not to trade through existing national best bid and offer quotations. These require a firm to identify, a trade relying upon such an exemption including settlement type, specifying one of the exceptions in Rule 611(b), whether the trade was reported late or executed outside normal market orders, and information referenced under NASD rules – e.g., vwap trades, stopped stock, etc.

http://www.nasd.com/web/groups/rules_regs/documents/notice_to_members/nasdw_019150.pdf