Polymarket Arbitrage Caveats
Last verified: 2026-06-30 PDT
Polymarket arbitrage is a high-intent phrase because it sounds simple: find a price gap, buy the cheap side, hedge the other side, and lock the difference. Real prediction-market work is not that clean. The displayed price is only the beginning. The actual question is whether the gap survives spread, depth, fees, settlement timing, resolution wording, and operational mistakes.
This guide is educational. It explains how to review apparent arbitrage without treating it as a promise, shortcut, or instruction to place trades.
Key definitions in plain English
- ▸Arbitrage: a price difference that appears to allow offsetting positions with limited directional exposure.
- ▸Spread: the gap between the best bid and best ask.
- ▸Depth: how much size is visible at each price level in the order book.
- ▸Resolution risk: the chance that two markets that look similar resolve under different wording, sources, or timing.
- ▸Execution risk: the risk that one leg fills and the other leg does not fill at the expected price.
- ▸Settlement timing: when funds or positions become reusable after resolution or sale.
Why apparent arbitrage can disappear
A Polymarket price is usually quoted in cents. A Yes share around 42 cents implies roughly 42% market-implied probability before spread and liquidity caveats. If another related market appears to disagree, the first instinct is to call it a gap. The better instinct is to write down the full path.
Example: Market A has Yes offered at 42 cents. Market B has a related No offered at 55 cents. On a screenshot, that can look like a 3-cent opportunity. But if the bid/ask spread is wide, available size is small, or the rules are not identical, the clean number can be an illusion.
The five checks before trusting a gap
- ▸Question match: Are the market questions truly the same economic event?
- ▸Source match: Do they use the same resolution source or the same source hierarchy?
- ▸Time match: Do deadlines, cutoffs, time zones, and event windows line up?
- ▸Book match: Is there enough size at the displayed prices for the whole plan?
- ▸Cost match: Do spreads, fees, bridging costs, and funding delays erase the edge?
If any answer is unclear, the safer label is not arbitrage. The safer label is unresolved basis risk.
A simple worksheet
Use this before calling anything an opportunity:
- ▸Market A URL, question, outcome, bid, ask, visible size
- ▸Market B URL, question, outcome, bid, ask, visible size
- ▸Resolution source for each market
- ▸Deadline and time zone for each market
- ▸Expected entry price after crossing spreads
- ▸Worst-case partial-fill scenario
- ▸Exit plan if one leg fills and the other moves
- ▸Review note after resolution
Common mistakes
- ▸Ignoring market wording. Similar wording is not identical wording.
- ▸Using mid-price instead of executable price. Mid-price can make a gap look cleaner than the order book allows.
- ▸Overlooking partial fills. One filled leg can create exposure the user did not intend.
- ▸Skipping settlement timing. Locked capital changes the real return profile.
- ▸Treating a bot as protection. Automation can amplify mistakes if caps, cancel rules, and audit logs are weak.
Bucko review workflow
Bucko can help as the notes-and-guardrails layer around prediction-market research:
- ▸Save both market URLs and screenshots.
- ▸Record bid, ask, spread, depth, timestamp, and source link.
- ▸Write the exact thesis and the exact invalidation condition.
- ▸Add exposure caps and a manual review checkpoint.
- ▸Review the outcome after resolution and tag what was missed.
Polymarket CTA
If you are eligible for the US app offer, use code BUCKO for a $50 deposit bonus on the Polymarket US app: https://www.poly.market/BUCKO. Confirm current eligibility, app screens, and offer terms before depositing.
Sources and last-verified notes
- ▸Polymarket docs checked 2026-06-30 PDT: trading overview, order creation documentation, market-data fetching documentation, and public Gamma API surfaces at docs.polymarket.com.
- ▸Polymarket Gamma public-search samples checked 2026-06-30 PDT; samples surfaced sports prediction-market regulation, app-store ranking, crypto, macro, AI leaderboard, and multi-outcome event structures.
- ▸Bucko/Polymarket partner offer wording is user-provided: code BUCKO, $50 deposit bonus for eligible U.S. app downloads, https://www.poly.market/BUCKO. No newer official affiliate term sheet was independently located during this run.