Prediction markets explained: how event contracts work and what to check before trading

On a prediction market you buy and sell shares in the outcome of real events at prices set by other traders, not by a bookmaker in Lagos or London. That strips out the margin and hands you a set of risks betting never had. This guide covers both sides.

By CasinoTrust Editorial TeamUpdated 31 August 20269 min readFact-checked against the Ranking Protocol

A prediction market is an exchange for event contracts. Each contract pays $1 if the event happens and $0 if it does not, and trades somewhere between those two numbers until it resolves. A "Yes" share changing hands at $0.62 means the crowd collectively puts the probability at 62%. You are trading against other participants; the platform earns a fee rather than a margin and does not care which side wins. That structure gets you closer to a fair price than anything else in this industry — and hands you risks no customer of a Nigerian betting shop has ever had to think about. This page belongs to our casino online reviews and pairs with the prediction market comparison.

How prediction markets differ from a bookmaker

At a bookmaker you bet against the house at a price the house wrote, margin included. On a prediction market you trade against other people at a price the order book produced. Everything else follows from that one difference.

Reading a price as a probability

When Yes trades at $0.62 and No at $0.39, the pair adds to $1.01 — that one cent is the spread, the market's version of a bookmaker's overround. On liquid markets the spread often sits under 1%; on thin ones it stretches to 5–10%, which is worse than any decent bookmaker. In decimal odds, $0.62 is 1 / 0.62 = 1.61. The expected-value maths is identical to betting: you make money when your probability estimate beats the market's. The extra option is that you can also buy at $0.62 and sell at $0.70 long before the event resolves, and take the profit without waiting for the result.

How we rank prediction markets

Our Ranking Protocol dimensions are adapted here, because prediction markets carry no house edge, no RTP and no bonuses worth mentioning. Liquidity and fees stand in for games and margins, while the resolution process and regulatory position stand in for licence tier at the heart of trust.

Fees and liquidity: where the real cost is hiding

Platforms advertise "no fees" or tiny fees, and that can be literally true while the trading still costs you plenty. Three costs count. The spread: on a market holding $2,000 of resting orders, a $500 buy pushes the price against you, and that slippage is the true fee. Trading fees: some venues take a percentage of profit or of the trade, so check whether it lands on makers, takers or both. Withdrawal costs: on-chain platforms make you pay network gas and normally hold crypto, while regulated US platforms move money by bank transfer with delays of their own. We measure all three across a standard basket of markets on test day.

Resolution risk: the risk a bookmaker never gives you

A Super Eagles fixture ends with a scoreline. "Will X happen by 31 December?" ends with a resolution rule written by a person, read by a resolver, and occasionally fought over. Markets have settled on technicalities — the literal wording of the question rather than the obvious intent behind it — and markets running on decentralised oracles have had outcomes challenged by token holders with money riding on the answer. Before you touch any contract, read the resolution criteria end to end, work out who decides and which source they will use, then discount your edge by the chance that the thing resolves in a way you never saw coming. Woolly wording is reason enough to skip a market, no matter how mispriced it looks.

Regulation: CFTC-registered venues against offshore ones

In the United States, event contracts sit with the Commodity Futures Trading Commission. Kalshi is a CFTC-registered designated contract market that takes US customers with full identity verification, bank funding and customer-fund protections on a par with a brokerage; it is the regulated route for US residents and we mention it here without linking, since we have not finished a test cycle on it. Polymarket's US entity is now CFTC-regulated after buying a licensed exchange, while its global on-chain venue runs with no gambling or financial licence and shuts out US users. In Nigeria, as in most countries, there is no dedicated framework: event contracts are not obviously within the National Lottery Regulatory Commission's remit, nobody has ruled clearly on them, and access to any given venue from here varies — check before you fund an account. A regulated venue gives you somewhere to complain and protection for your money; an on-chain venue gives you self-custody and nobody to call.

What to check before you trade

• Published resolution rules on every market, naming both the resolution source and the decision process
• A dispute mechanism with a track record you can actually read, not merely a paragraph describing one
• Order-book depth visible before you trade, so the real cost of your position is on screen
• A clear regulatory position for your country and geo-restrictions that are genuinely enforced
• Fees listed in full: trading, withdrawal, network, inactivity
• Self-custody (on-chain) or segregated customer funds (regulated) — you should know which one applies
• The ability to sell before resolution at a sensible spread, rather than being stuck holding to settlement

Red flags on a prediction market

• Markets whose resolution criteria rest on a subjective judgement or a source nobody has named
• A history of resolutions reversed or contested in ways that paid the platform or its token holders
• Liquidity that is mostly the platform's own market-maker, which can pull out without warning
• Promotional "free money" markets or airdrop incentives that pull in wash trading and bend prices
• No stated policy on insider trading by people who know something about the event that the public does not
• Any nudge towards using a VPN to get around geo-restrictions — a breach that can void your positions
• Any venue holding your funds with neither regulation nor on-chain transparency behind it

If prediction markets are new to you

Approach it as trading, not as betting. Begin with the probability conversion — a $0.25 share needs the event to land more than 25% of the time before you profit — and size positions so that a market going against you, or resolving in a way nobody expected, does not wipe you out. The staking discipline in our bankroll management guide carries over unchanged. If you are arriving from the betting shop, read our sports betting reviews next to this page and watch where bookmaker prices and market prices pull apart, because that gap is often where the value lives. The Academy works through expected value properly, and the principle does not change whether the instrument is a blackjack hand or an election contract.

The reviewed platform in brief

Polymarket

Polymarket is the largest prediction market by volume and the most liquid on big political and macro questions, where spreads usually run to a cent or two. It runs on Polygon in USDC, so the global venue has no fiat on-ramp — funding from Nigeria means buying USDC, typically P2P, and bridging it in yourself — funds stay self-custodied, and withdrawals are instant once a market resolves. Resolution goes through a decentralised oracle with a dispute process, which has produced contested outcomes on loosely worded markets, so read every contract's rules. The US entity is now CFTC-regulated; the global venue is not and excludes US residents. There is no live chat. Read the full Polymarket review.