Contract specification

The reference document for a single instrument, published per instrument by the venue or the firm and read from there rather than inferred from a general rule about the asset class. The fields that decide how a position behaves are the contract size, the tick size and its value, the smallest and largest volume a single instruction may be written in, the step between permitted volumes, the quoted trading hours, the currency the instrument settles in, and the margin requirement expressed as a percentage of notional value.

Several fields carry conditions rather than constants. Margin requirements are commonly raised ahead of weekends, long public holidays and the run up to expiry on contracts written on futures. Trading hours change where an underlying venue changes its own. An expiry date applies to any instrument written on a dated contract, together with the stated treatment as that date approaches. A specification therefore describes a schedule as much as a set of numbers.

The commonest way a position ends up a different size from the one intended is a figure carried across from a different instrument, because contract sizes vary by class and sometimes within a class. The platform a YAL account runs on, MetaTrader 5, publishes these fields per instrument in its own interface, so the platform's own reference is the one that governs what a number entered there means.