Written by GammaPredict Research · · How we score

Last expanded September 2026 · Models, not a live rate card · Responsible use

What this page is for

This is the risk checklist. The fees comparison holds official schedule links. The fees-and-spreads briefing is the short news version. Do not treat a cropped mid as your expected return.

A 50¢ Yes is a quote, not a 50% payout. Between that print and cash sit the spread, any taker fee on the ticket, the deposit rail, and whether you can exit before resolution.

Worked example — mid is not a fill

Suppose a market shows 50¢ mid. You want 100 Yes shares. The best ask is 52¢ and the best bid is 48¢. Getting in costs $52. Selling immediately at the bid returns $48. The 4¢ round-trip is 8% of that notional before any venue fee the ticket adds.

If the live ticket then adds a taker charge — Kalshi and fee-enabled Polymarket categories can — that is a second line. We do not invent the percentage. Read Kalshi’s fee schedule ↗ or Polymarket trading fees ↗ for the market you would actually trade. A thin book can cost more than that published fee. Use the liquidity guide next to this page.

Fee types to check on the ticket

  • Execution / maker-taker. Shown on the trade ticket. Category rules change. Polymarket documents fee-enabled vs fee-free categories separately. Kalshi varies by contract. Smarkets charges commission on net winnings under its standard model.
  • Bid–ask spread and depth. Often larger than the explicit fee. If you cannot exit, you do not have a trade.
  • Deposit and withdrawal. ACH holds, card processors, network gas, bridges, minimums. A “cheap” fill that takes three days to leave is not cheap.
  • FX or stablecoin conversion. Wallet venues price in the listed token. Bank venues price in the listed fiat. Mixing them in a screenshot comparison is how people invent a winner.

Risk checklist

  • Resolution risk. Unclear wording or a source that can be edited. Read the resolution briefing before you size a mid.
  • Liquidity risk. Headline politics books are not the long tail. Check size at the touch, not just last price.
  • Custody risk. Keys and smart contracts vs a custodial cash account vs play-money. Manifold is the practice board, not a cash substitute.
  • Regulatory / access risk. The same headline can be two legal products. Access and KYC and Regions exist for that. We do not publish VPN workarounds.
  • Information risk. Markets can be wrong for a long time. A 12% Yes on a thin book is not a 12% fill.

Position sizing

Treat the first trades as tuition. Prefer liquid markets. Read the resolution source twice. Never size as if the price is certain. If you cannot explain the settlement source in one sentence, you do not have a view — you have a comment. Mechanics sit on how prediction markets work.

Compare two venues on the same hypothetical order: displayed fee, best bid/ask, filled size, withdrawal path. Then open Polymarket vs Kalshi or the top prediction markets ranking for the shortlist — not a tweet.

Official fee sources → Liquidity guide Desk briefing

FAQ

Do you publish a live fee table?

No. Operators change schedules by category and date. Compare fee models and the live ticket. The comparison page links official sources.

Is a 50¢ share a 50% expected return?

No. Spread, fees, lock-in and resolution rules sit between the quoted probability and what you keep. The worked example above is arithmetic, not a promise.

Where should I compare costs next?

Open the fees comparison and liquidity guide, then two platform profiles side by side.