Trades REPORTED after hours do not always OCCUR after hours.

"a. The first category is sometimes used by financial institutions that are non-market makers to report larger transactions that actually occurred during market hours. However, since these institutions do not have access to ACT (Automated Confirmation Transaction Service), they use "Form T" to report.

MMs are prohibited from habitual "Off Market” transactions:

A pattern or practice of late reporting without exceptional circumstances may be considered conduct inconsistent with high standards of commercial honor and just and equitable principles of trade, in violation of Rule 2110.

These ”Off Market” trades are typically used by larger investors to trade larger lots at pre-arranged prices without risk of driving the price upward or downward.

b. The second category involves so called “ex-clearing” lots. Certain transactions may clear and settle outside of the regular clearing system ("ex-clearing" transactions), where two dealers make an arrangement to settle trades between themselves and outside the clearing system.