Trading and fees

Binary options use the same CreateOrder, ModifyOrder and CancelOrder transactions and the same SDK / WASM signer calls as other markets. Pass the binary options market_id and:

Place an order

Python

Use an initialized SignerClient from Signing transactions. Set MARKET_ID to a current binary options market ID from Discover markets.

tx, tx_hash, err = await client.create_order(
    market_index=MARKET_ID,      # market_id from /api/v1/events
    client_order_index=1234,
    base_amount=1000000,         # 100.0000 shares
    price=51,                    # 0.51 USDC per Up share
    is_ask=False,                # buy = Up
    order_type=client.ORDER_TYPE_LIMIT,
    time_in_force=client.ORDER_TIME_IN_FORCE_GOOD_TILL_TIME,
    reduce_only=False,
    order_expiry=client.DEFAULT_28_DAY_ORDER_EXPIRY,
)

TypeScript (WASM)

This snippet uses the signer and submission helpers from the TypeScript quickstart.

const tx = check(lighter.SignCreateOrder(
  MARKET_ID, clientOrderIndex, 1000000, 51, 0 /* buy = Up */, 0 /* limit */, 1 /* GTT */,
  0, 0, orderExpiry,
  0, 0, 0,                    // integrator account, taker fee, maker fee
  0, 0, 0, nonce, API_KEY_INDEX, ACCOUNT_INDEX,
));
await sendTx(tx);

Order rules

• Create and modify requests must pass the same trading-window, frozen-book and price-cap checks: start_timestamp ≤ block time ≤ end_timestamp, is_frozen = false, and 0 < price < settlement_cap. A start_timestamp of 0 means trading can start from listing. Cancellation is allowed outside the trading window.
• For resting orders, buy cost is P × size and sell cost is (1 − P) × size, where P is the Up price in USDC and size is shares. The USDC reserve is calculated per market as max(Σ buy costs − Down shares held × 1.00, Σ sell costs − Up shares held × 1.00, 0). Buy and sell requirements are not added together; existing shares offset the opposite side. IOC and market orders are funded at fill time.
• The min_quote_amount check uses P × size for both buys and sells, even though opening a Down position costs (1 − P) × size. Read both minimums from events. For example, mainnet markets checked on October 19, 2026 have min_base_amount = 5 shares and min_quote_amount = 0.000001 USDC. A 5-share sell at P = 0.02 has an Up notional of 0.10 USDC and passes that quote minimum; its Down cost is 4.90 USDC. In this configuration the 5-share base minimum is the binding minimum. Also respect order_quote_limit.
• A market order's price is the worst acceptable Up price, as on other markets.
• Public pool and insurance fund accounts cannot trade binary options.

Errors

Orders and trades

accountActiveOrders, accountInactiveOrders and trades accept market_type=bo (all by default) and work with a binary options market_id. Trades carry market_kind: "bo". Settlement records use type: "market-settlement"; see Positions and settlement.

recentTrades returns an empty list once a binary options market has settled. Use trades with market_id for historical fills and settlement records. exchangeStats includes binary options symbols such as ETH-UPDOWN-…; filter its market entries by symbol when separating market types.

Fees

Each market has a maximum taker_fee and maker_fee (Up/Down series: taker 1%, maker 0%). Both sides pay in USDC on the trade notional, scaled by the trade price and by the account's binary options fee multiplier:

fee = marketFee × bo_fee_rate × size × P × (1 − P)

Use decimal rates in the formula: marketFee = 0.01 for a 1% market fee. P is the Up price in USDC (0.51, not 51 price ticks).

• size × P is the Up-price notional in USDC. Opening Down costs (1 − P) × size; resting-order reserves follow the per-market rule above. Use the same fee formula for both sides.
• (1 − P) makes fees smaller as the outcome becomes certain: highest at P = 0.50, near zero at 0.01 and 0.99.
• bo_fee_rate is the account's multiplier, the product of its binary options volume tier and LIT staking tier, 1 by default.

Binary options fees are separate from the perps/spot account tiers. feeTiers with filter=bo returns the bo_tiers (by trailing volume) and staking_tiers tables; accountLimits returns the account's bo_user_tier_name and bo_fee_rate. Read the current tables from the endpoint instead of hard-coding volume thresholds or staking discounts.

curl "https://mainnet.zklighter.elliot.ai/api/v1/feeTiers?filter=bo"

Fees in trade responses

In trade JSON, taker_fee / maker_fee are the effective rate in fee ticks (1e6 = 100%): with bo_fee_rate = 1, a 1% market taker fee on a fill at 0.51 shows as taker_fee: 4900 (10000 × (1 − 0.51)), i.e. 51.00 × 0.49% = 0.2499 USDC on 100 shares.