Why it matters
Post-only helps control fees and reduces accidental market orders. It forces patience into your execution logic.
Operational use: this is how the market taxes urgency. When it appears, slow down or size down.
Common trap
Using post-only during fast moves. The order can be rejected repeatedly, meaning you don’t actually participate when the market is moving.
Example
Price moves quickly toward your level. Your post-only order keeps getting rejected because it would cross. You miss the fill and then chase later at worse prices.
Operational cue: if you can’t point to it on the chart, in the DOM, or in your broker logs, treat it as a story and trade smaller.
Notes
Quick rule
- If you see this repeatedly, you are in a different regime than your model assumes.
- Regime change usually means position size change.
- When in doubt: trade smaller, or don’t trade.