alpaca-broker-trading-orders

Submit a POST to /v1/trading/accounts/{account_id}/orders with a decimal qty or notional string, type market, and time_in_force day. The asset must have fractionable set to true, and fractional sells cannot be shorted.

Fetch pending invest instructions from your database, check each account's buying power, place a notional market day order per instruction with a unique client_order_id, and mark instructions done only after a successful create. Schedule the batch shortly before market open.

qty specifies a share quantity while notional specifies a dollar amount, and they are mutually exclusive — supplying both returns a 400 error. Both accept up to 9 decimal places, and notional orders are limited to market and limit types with day time-in-force.

Alpaca rejects orders that could self-cross with an existing opposite-side order at crossable prices, returning a 403. Use bracket, OCO, or trailing-stop orders for simultaneous take-profit and stop-loss, since those are exempt from the wash-trade check.

Notional orders cannot be replaced — you must cancel and resubmit them. Fractional qty values also cannot be changed on replace, and replacement is blocked while an order is in accepted, pending_new, pending_cancel, or pending_replace states.

accepted means Alpaca received the order but has not routed it, new means it is routed to exchanges, and pending_new means routed but not yet accepted for execution. Treat all three as in-flight and track terminal states like filled, canceled, or rejected via the trade-events stream.