Gambling Online 101
beginner
6 min readTrading on Outcomes
How to buy and sell yes/no contracts.
BonusBell Team
Prediction market trading lets you buy and sell contracts on real-world outcomes. Unlike traditional betting, you can exit positions before events resolve — taking profits or cutting losses as probabilities shift.
How Contracts Work
Each contract represents a Yes or No position:
- Yes shares pay $1.00 if the event happens
- No shares pay $1.00 if the event doesn't happen
- The clean event space sums to $1.00 at resolution, but the displayed quotes can deviate because of spreads and fees
Contract Pricing
If Yes = $0.62, then No ≈ $0.38=Market implies 62% probability event occurs
That 62-cent contract means you are risking $0.62 to win $0.38 if the event resolves Yes. The displayed bid/ask spread and any platform fee are the trading friction layered on top.
Price It: Prediction Market Contract Lab
Market vs your number
Market-implied probability
62.0%
Edge per share
+$0.08
Max loss
$62.00
Max profit
$38.00
Expected value on this position
+$8.00
The market is only a price. Your edge exists when your probability estimate is better than that price.
Reading the Order Book
Like stock trading, prediction markets have bid/ask spreads:
- Bid – Highest price someone will buy at
- Ask – Lowest price someone will sell at
- Spread – Difference between bid and ask
Good to Know
Liquidity matters. Popular markets have tight spreads ($0.01-$0.02). Obscure markets might have $0.05+ spreads, eating into profits.
Practice It: Order Book Fill Lab
Bid / ask spread
3.0c
Market-order average fill
65.4c
If you cross the spread now
$49.05 total cost
If your order is larger than the top ask size, you pay up into the next price level. That is slippage, and it quietly changes your edge.
If you use a limit order
No immediate fill
Your price is inside the spread, so you are waiting for someone to hit your bid.
Buying to Open
To enter a position:
- Decide if you believe Yes or No is more likely
- Buy the shares at the ask price (or place limit order)
- Pay the contract price per share
- Hold until resolution or sell to exit
Buy Example
Buy 100 Yes shares at $0.40=Cost: $40 | Max Profit: $60 | Max Loss: $40
If event happens, shares pay $1.00 each = $100 return.
Selling to Close
The key difference from traditional betting—you can exit early:
Exit Scenarios
| Situation | Action | Result |
|---|---|---|
| Price rose to $0.70 | Sell at bid | Capture $0.30 profit/share |
| Price dropped to $0.25 | Sell at bid | Cut loss at -$0.15/share |
| Wait for resolution | Hold | Get $1.00 or $0.00 |
Strategy Insight
Think of contracts like stocks. You don't have to hold to expiration— take profits when the market moves in your favor.
Short Selling
To bet against an outcome, you can:
- Buy No shares – Pay for "it won't happen"
- Sell Yes shares short – Borrow and sell, buy back later (if supported)
Pro Tip
Most platforms simply let you buy No shares rather than complex shorting. The math is the same—you profit when the event doesn't occur.
Resolution Rules Matter as Much as Price
Before you trade, read the market rules. Event contracts are only as good as their resolution criteria. Two markets that look identical at headline level can settle differently if one uses a government release, another uses a media source, and a third has special rules for delays, recounts, or cancellations.
- Check the source of truth. What exact publication or data feed resolves the contract?
- Check edge cases. Delays, voids, ties, overtime, and recounts can all matter.
- Check fees and settlement timing. A good price is less attractive if the venue is slow or expensive to exit.
Limit Orders vs Market Orders
Order Types
| Order Type | Fills At | Best For |
|---|---|---|
| Market | Current ask (buy) or bid (sell) | Speed, liquid markets |
| Limit | Your specified price or better | Patience, volatile markets |
Trading Strategies
Momentum Trading
Buy when probability is trending in one direction:
- News breaks that increases likelihood
- Ride the wave as market reprices
- Exit before full resolution to capture estimated gains
Mean Reversion
Fade overreactions:
- Market panics on rumors or partial information
- Buy the overreaction if you believe it's excessive
- Profit as market normalizes
Arbitrage
Look for price discrepancies:
- Yes + No combined price differs from $1.00 significantly
- Same event priced differently across platforms
- Rare but low-variance when found
Platform Considerations
- Fees – Trading, settlement, or withdrawal fees vary by venue.
- Settlement – Some contracts resolve quickly; others tie up capital for months.
- Disputes – What happens if the outcome source is ambiguous or delayed?
- Liquidity – Can you actually enter and exit at a fair price without slippage?
Related Reading
- What Are Prediction Markets?— the category-level primer on event pricing, contract structure, and venue differences
- Cross-Market Arbitrage— what happens when the same event is priced differently across prediction venues and sportsbooks
Key Takeaways
- 1Contracts are Yes/No shares that pay $1 or $0 at resolution
- 2You can sell before resolution to capture gains or cut losses
- 3Bid/ask spread is the cost of trading—liquidity matters
- 4Use limit orders in volatile or low-liquidity markets
- 5Think like a trader: momentum, mean reversion, arbitrage
Sources & References
- Kalshi’s public help materials document binary contract payouts, order types, and exchange fees for US-regulated event contracts. (Kalshi Help Center)
- Polymarket’s public help materials explain order-book mechanics, fees, and market structure for its event contracts. (Polymarket Help Center)
- Order-book concepts such as bid, ask, spread, market orders, and limit orders follow standard exchange mechanics and remain the right framework for understanding slippage in outcome trading.
- Efficient Market Hypothesis (Fama, 1970). Arbitrage pricing theory still applies to prediction markets whenever the cost of covering all outcomes is below the locked payout.
Mathematical claims are independently verifiable. BonusBell platform analysis reflects our tracked platform directory and dated evidence checks as of March 2026.