Market orders
All trades on Theta Labs are submitted as market orders — they execute immediately at the best available price. When you place a trade, the platform:- Checks the current best ask (for buys) or best bid (for sells)
- Submits your order to the exchange
- Fills as much as possible at the current price, then continues at the next available price level if needed
The orderbook
Both Polymarket and Kalshi use limit-order-based books, but the underlying mechanics differ:Polymarket (CLOB)
Polymarket uses a Central Limit Order Book (CLOB). Orders sit in the book as bids and asks. When you place a market order to buy, it matches against the lowest available ask. The CLOB is off-chain for matching but settles on-chain on Polygon.Kalshi
Kalshi uses a traditional exchange orderbook with limit orders. The bid-ask spread tends to be slightly wider on less liquid markets. Kalshi trades settle directly on Solana via USDC.Reading the spread
The bid-ask spread is the difference between what sellers want and what buyers are offering:- Bid = the highest price someone is willing to buy at
- Ask = the lowest price someone is willing to sell at
- A narrow spread (e.g., 39¢ bid / 41¢ ask) means a liquid market — you can trade near the fair value
- A wide spread (e.g., 30¢ bid / 50¢ ask) means the market is thin — large orders will move the price significantly
Slippage
Slippage occurs when your order fills at a different price than expected. It happens when:- The market moves between when you click and when the order reaches the exchange
- Your order is large enough to consume multiple price levels in the orderbook, so later fills occur at worse prices
Minimizing slippage
| Situation | What to do |
|---|---|
| Wide bid-ask spread | Break a large order into smaller ones over time, or accept the wider cost as part of the trade |
| Low-volume market | Expect more slippage; size positions smaller |
| Fast-moving market | Prices update in real time — if a market is rapidly moving, your fill may differ from what you see |
Position sizing
A few practical rules for sizing your trades:- Never risk more than you’re prepared to lose entirely. Even high-probability markets can resolve unexpectedly.
- Spread across markets rather than concentrating a large position in one. This reduces the impact of a single bad outcome.
- Start small on new markets. Until you understand a market’s liquidity and spread behavior, keep initial positions small.
- Account for the spread cost. If you buy at 41¢ and the bid is 39¢, you’re starting 2¢ in the hole. Factor this into your expected return.
Options trades on Theta Labs execute instantly against the platform market maker at a quoted price — there is no orderbook slippage for options. The price you see in the trade modal is the price you pay.