Create Margin FCM Position Transfer

Endpoint for FCM members to move a perps position in one market from one of their subtraders into a subtrader under their FCM’s error account.

This endpoint must be enabled for your FCM by Kalshi. Kalshi enables it by configuring the error account that receives transferred positions and gives you that account’s user id, which prefixes target_subtrader_id. Contact Kalshi to enable it; until then, requests return 400. Position transfers are also switched on per exchange; while they are off, requests return 409.

• The destination is always your FCM’s error account. target_subtrader_id picks the subtrader under it, which is created on first use.
• Each request moves one market for one source subtrader. To move many positions, send one request per subtrader and market.
• No cash moves when a transfer is booked. Both sides’ positions and cost basis change as for a fee-free trade at price: the source closes at price and the error account opens at price. Both settle in the next settlement cycle: the source realizes the difference between price and the market’s last settlement mark, and the error account’s variation margin runs from price to the next settlement mark. To make a customer whole, use the price of the fill being reversed.
• side and count describe the position being moved: long moves a long of count contracts, short moves a short. count must be a whole number of contracts. The source’s current position is not checked; moving more than it holds, or the other side, flips or grows its position.
• client_transfer_id makes the request idempotent per source subtrader: once a transfer with that id has been booked from source_subtrader_id, a later request with the same id from that subtrader, to any target, books nothing unless the exchange has restarted in between. The exchange checks the id only after it re-checks the transfer switch, trading status and both accounts’ current risk, so a repeat returns 409 with error code transfer_already_applied only when it passes those checks. Otherwise it gets the error for the check it failed, such as 400 insufficient_balance once the earlier transfer has used the error account’s margin, or 409 while trading is paused.
• After a timeout or 5xx, retry with the same id. transfer_already_applied confirms that the earlier attempt was booked. Any other error refuses only the retry and leaves the earlier attempt’s outcome unknown: check the source subtrader’s position before you send the transfer again under a new id.
• The exchange does not keep transfer ids across a restart, such as a maintenance window, so a retry sent after one can book the transfer a second time. If the exchange may have restarted since the first attempt, check the source subtrader’s position before retrying, even with the same id.
• The market must have traded at least once and trading must not be paused; otherwise the request returns 409. Both accounts must also pass the exchange’s risk checks for their post-transfer positions (available margin, FCM initial-margin caps, notional risk limits); a failed risk check returns 400 with the exchange’s reason, such as insufficient_balance, and a blocked account returns 409.
• Transfers appear on the daily statement and in the position_transfer_audit report. They never appear as fills or in trade_audit.

Example. A customer subtrader holds 10 long in KXBTCPERP, filled at $63,000. Send `side` `long`, `count` `10`, `price` `63000.00`: the customer goes from 10 long to flat and the error account subtrader from flat to 10 long, both at$63,000, with no cash moving.