Amend Order (V2)

Endpoint for amending the price, max fillable count, and/or expiration time of an existing event-market order. The request count is the updated total/max fillable count, equal to already filled count plus desired resting remaining count. This behavior matches the v1 amend endpoints; only the request/response shape differs.

POST /portfolio/events/orders/{order_id}/amend

Amend Order (V2)

cURL

curl --request POST \
  --url https://external-api.kalshi.com/trade-api/v2/portfolio/events/orders/{order_id}/amend \
  --header 'Content-Type: application/json' \
  --header 'KALSHI-ACCESS-KEY: <api-key>' \
  --header 'KALSHI-ACCESS-SIGNATURE: <api-key>' \
  --header 'KALSHI-ACCESS-TIMESTAMP: <api-key>' \
  --data '
{
  "ticker": "HIGHNY-24JAN01-T60",
  "side": "bid",
  "price": "0.5700",
  "count": "8.00",
  "client_order_id": "8c35ecb3-328f-4f52-8c7c-0f4b9862f8d1",
  "updated_client_order_id": "2a0e3fc9-b593-4aa3-96e5-82f7f7566c2a",
  "exchange_index": 0
}
'

200

{
  "order_id": "3b23c1c7-f4ef-4f0d-8b9a-9e53c61f1a0d",
  "client_order_id": "2a0e3fc9-b593-4aa3-96e5-82f7f7566c2a",
  "remaining_count": "8.00",
  "fill_count": "0.00",
  "ts_ms": 1715793690123
}

Amending only expiry or decreasing size preserves queue position. Increasing size or changing price forfeits queue position and places the order at the back of the queue.

Authorizations

KALSHI-ACCESS-KEY · string · header · required

Your API key ID

KALSHI-ACCESS-SIGNATURE · string · header · required

Base64 signature of the pre-sign text (timestamp + method + path) made with the API key's algorithm - RSA-PSS with SHA-256 for RSA keys, Ed25519 for Ed25519 keys

KALSHI-ACCESS-TIMESTAMP · string · header · required

Request timestamp in milliseconds

Path Parameters

order_id · string · required

Order ID

Query Parameters

subaccount · integer

Subaccount number (0 for primary, 1-63 for subaccounts). Defaults to 0. Subaccount-restricted API keys default to their locked subaccount and must omit this parameter or pass their locked subaccount.

Required range: x >= 0

Body

application/json

ticker · string · required

Market ticker

side · enum<string> · required

Side of the order

Available options: bid, ask

price · string · required

Updated price for the order in fixed-point dollars.

Example:

"0.5600"

count · string · required

Updated total/max fillable count for the order. Set this to the order's already filled count plus the desired resting remaining count after the amend.

Example:

"10.00"

client_order_id · string

The original client-specified order ID to be amended

updated_client_order_id · string

The new client-specified order ID after amendment

expiration_time · integer<int64>

New Unix expiration timestamp in seconds. Omit to preserve the current expiry, or use 0 to remove it (good-till-canceled). A nonzero expiry must be in the future. Send the current price and total quantity for an expiry-only amendment; this preserves queue position.

Required range: x >= 0

exchange_index · integer

Exchange shard index. If omitted, auto-routes when ticker is provided; otherwise defaults to 0. Use -1 to require auto-routing by ticker.

Example:

0

Response

200

application/json

Order amended successfully

order_id · string · required

ts_ms · integer<int64> · required

Matching engine timestamp at which the amend was processed, as Unix epoch milliseconds.

client_order_id · string

remaining_count · string | null

Number of resting contracts remaining after the amend. This is the actual post-amend resting quantity, not the request's total/max fillable count. Only present when the amend caused a fill or changed the resting size.

Example:

"10.00"

fill_count · string | null

Number of contracts filled as a result of the amend crossing the book. Only present when fills occurred or remaining size changed.

Example:

"10.00"

average_fill_price · string | null

Volume-weighted average fill price for fills resulting from the amend. Only present when fills occurred.

Example:

"0.5600"

average_fee_paid · string | null

Volume-weighted average fee paid per contract for fills resulting from the amend. Only present when fills occurred.

Example:

"0.5600"