Positions and portfolio

Positions and profit and loss derived from fills only.

Rule

Each instrument has one net position. A position is never edited directly; it changes only through fills.

Profit and loss

Closing quantity is matched against open lots first in, first out, so realised profit and loss is exact integer arithmetic. Commissions are tracked separately. Unrealised profit and loss is marked at the side the position would close on.

Planned

Margin accounts, per-venue fee models beyond a basis-point commission, and exposure across venues.