KuCoin responds with code and msg fields: code 200000 means success, anything else is a rejection. Codes are six-digit numbers, and a rejection often comes with HTTP status 200, so you need to look at the code. KuCoin spot and futures are separate APIs with different code sets: for example, insufficient balance is 200004 on spot and 300003 on futures.

A KuCoin key has three parts — key, secret and passphrase — and any of them can be wrong. If the terminal doesn’t recognize the rejection, the popup after “Order:” shows the exchange’s response verbatim: KuCoin API 200004: Balance insufficient or KuCoin POST /orders HTTP 400: {"code":"…","msg":"…"}. See Error messages: how to read them for the general approach, and Connecting exchanges and API keys for key setup.

What the terminal explains itself

An IP whitelist rejection (400006) or key permission rejection (400007) comes through as exchange text in the order message: the key itself is correct. But if the exchange rejects this way already at connection time, the terminal can show the same “exchange rejected API key or secret” card — so when you see it, also check the key’s permissions and IP whitelist.

Common codes

Fixing common problems

Exchange rejected the key

The rejected-key card appears once per connection. Once the connection comes up with a fixed key, the terminal can show it again if the key stops working again.

Permissions and IP whitelist

Codes 400006 and 400007 mean the key is correct, but the exchange is blocking the request. For 400006, add your computer’s external IP to the key’s whitelist; if the connection goes through a proxy (the Proxy section in the connection card), add the proxy address instead. For 400007, enable trading permission on the key for the required market. You usually don’t need to recreate the key: permissions and IP list are changed in the existing key’s settings.

Insufficient balance

On spot (200004), funds locked by open orders are not available for a new order. Cancel extra orders or reduce the quantity.

On futures (300003), funds must be on the KuCoin futures account. KuCoin keeps spot and futures accounts separate — transfer funds between them on the exchange website.

When closing a spot position with a sell, the shortfall often comes from the fee charged in the purchased coin. The terminal accounts for this: it re-reads the wallet and retries the sell with a slightly smaller quantity. After that, the wallet may hold “dust” smaller than the volume step — you can’t sell it with an order.

Futures volume

KuCoin futures orders are counted in contracts, not coins: each contract has its own size. The terminal converts the volume from coins to contracts itself and rounds to the nearest whole number of contracts, but never below one. So an order smaller than one contract goes to the exchange as one contract — the actual volume will be larger than what you entered. On small accounts, check the coin’s contract size on the KuCoin website.

Rate limit exceeded

The terminal shows the UTC time until the restriction is active and waits out the pause itself. The limit counts per address: KuCoin connections to the same market through one IP or proxy share the same pool. If the restriction repeats, reduce the number of KuCoin windows and panels or spread connections across different proxies. See Terminal messages for more.

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