It stands for open price gap time in force; an order qualifier that is used to direct orders to the opening session (auction)- open price gap (OPG) or the time of a trading session that marks its opening or reopening. It indicates such orders that are directed to the opening auction. If not filled during the opening session, such orders, or part thereof, will expire. And if no uncrossing takes place during the opening auction, these orders will also expire.

An order is time in force (TIF) when it is time-bound: it comes with an instruction that limits the time it should be placed and/ or the period during which it remains in effect (in force) before it gets automatically cancelled.

An order will be rejected (not filled) if a security does not have a scheduled opening auction. An example is a primary only order (PO) posted for participation after the primary market opens is routed and executed as a normal market order. It combines a market order with the only opening (OPG) time in force (OPG TIF) to initiate an order that is automatically submitted at the market’s open and executes at the market price.

OPG orders may participate in the uncrossing of the opening auction and are incorporated in the calculation of the indicative auction information. The unfilled part of these orders
will expire at the end of the opening auction uncrossing.