MX2 Clarifies 'Post Only' Orders: Keeping Trades Fair and Smooth
Published Date: 11/21/2025
Notice
Summary
MX2 LLC is updating its rules to make it clearer how orders with a 'Post Only' instruction are handled, especially when combined with other order instructions. This change affects traders using MX2’s platform and helps ensure smoother, fairer order processing. The update is effective immediately, with no extra costs, and MX2 will announce the exact start date soon.
Analyzed Economic Effects
3 provisions identified: 2 benefits, 0 costs, 1 mixed.
Post Only Orders Can Remove Liquidity
If you trade on MX2, an order entered with a Post Only instruction can remove liquidity when the security is priced below $1.00 or when removing liquidity is economically beneficial to the firm entering the order. MX2 amended Rule 11.6(l)(2) to make clear this applies whether the order also included Display-Price Sliding, Cancel Back, or no additional instruction.
Cancel Back Instruction Will Cancel Immediately
If you attach a Cancel Back instruction to an order on MX2, the order will be immediately cancelled instead of re-priced when displaying it at its limit price would create a Rule 610(d) (Locked and Crossed Markets Rule) or Regulation SHO violation, or if it cannot otherwise be executed or posted. MX2 leaves this Cancel Back behavior unchanged while clarifying how Post Only orders interact with other instructions.
Clarification Effective Immediately, No Cost
MX2's rule amendment to Rule 11.6 became effective upon filing (filed September 30, 2025) after the SEC waived the 30-day delay, and the Exchange says no changes to trading systems or extra costs to members are expected. MX2 will announce the exact implementation start date via Regulatory Notice to members and sponsored participants.
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