IEX Updates Post Only Orders for Price Improvement Rules
Published Date: 5/7/2025
Notice
Summary
Investors Exchange (IEX) is updating its Post Only orders so they only remove liquidity if they get at least a 1-cent price improvement. This change affects traders using Post Only orders and aims to make trading fairer and smarter. The new rule is effective immediately, helping investors save money by avoiding less favorable trades.
Analyzed Economic Effects
3 provisions identified: 3 benefits, 0 costs, 0 mixed.
More Post Only Orders Will Post
Because IEX now requires at least $0.01 of price improvement for a Post Only order to execute on entry, many Post Only orders that currently execute on entry (for example, when available price improvement is $0.005) will instead post to the IEX Order Book and add displayed liquidity.
Post Only Orders Need $0.01 Improvement
IEX changed its Post Only order rule so an incoming Post Only order will only remove contra-side liquidity on entry if it would receive at least $0.01 of price improvement. Previously, some Post Only orders could execute on entry with only $0.005 of price improvement; Post Only orders on IEX are for shares priced at or above $1.00 per share.
Brings IEX In Line With Other Exchanges
IEX replaced its Sum of Fees test with an explicit $0.01 minimum price-improvement requirement, matching how Nasdaq and NYSE Arca treat incoming Post Only orders. The Exchange says this alignment promotes competition among equity exchanges and provides members greater determinism.
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