> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vos.verolabs.co/llms.txt
> Use this file to discover all available pages before exploring further.

# Order management

> Cancel and replace message contracts, validation rules, priority handling, and response flow

Use `OrderCancelRequest (35=F)` to cancel an active order.
Use `OrderCancelReplaceRequest (35=G)` to amend quantity or price for an active order.

## Cancel request fields

| Tag  | Name           | Req | Type         | Description                                                    |
| ---- | -------------- | --- | ------------ | -------------------------------------------------------------- |
| `41` | `OrigClOrdID`  | Y   | String       | Original client order identifier of the order being cancelled. |
| `11` | `ClOrdID`      | Y   | String       | New client identifier for the cancel request.                  |
| `55` | `Symbol`       | Y   | String       | Symbol code of the original order.                             |
| `54` | `Side`         | Y   | Char         | Original order side. Use `1=Buy` or `2=Sell`.                  |
| `60` | `TransactTime` | Y   | UTCTimestamp | Time when the cancel request is created.                       |

## Cancel response flow

| Step                                      | Response                                                                                    |
| ----------------------------------------- | ------------------------------------------------------------------------------------------- |
| Cancel request is invalid                 | `OrderCancelReject (35=9)` with the current order status and rejection detail.              |
| Cancel request is accepted for processing | `ExecutionReport (35=8)` with `OrdStatus (39)=6` and `ExecType (150)=6` for pending cancel. |
| Cancel succeeds                           | `ExecutionReport (35=8)` with `OrdStatus (39)=4` and `ExecType (150)=4` for canceled.       |
| Cancel fails after acceptance             | `OrderCancelReject (35=9)` with the current order status and rejection detail.              |

## Replace request fields

| Tag   | Name                | Req | Type         | Description                                                                                  |
| ----- | ------------------- | --- | ------------ | -------------------------------------------------------------------------------------------- |
| `41`  | `OrigClOrdID`       | Y   | String       | Original client order identifier of the order being amended.                                 |
| `11`  | `ClOrdID`           | Y   | String       | New client identifier for the replace request.                                               |
| `55`  | `Symbol`            | Y   | String       | Symbol code. This value must match the original order.                                       |
| `54`  | `Side`              | Y   | Char         | Order side. This value must match the original order.                                        |
| `60`  | `TransactTime`      | Y   | UTCTimestamp | Time when the replace request is created.                                                    |
| `38`  | `OrderQty`          | Y   | Qty          | New total order quantity.                                                                    |
| `40`  | `OrdType`           | Y   | Char         | Order type. This value is required in the message and cannot change the original order type. |
| `44`  | `Price`             | Y   | Price        | New order price.                                                                             |
| `59`  | `TimeInForce`       | N   | Char         | Order validity. This value cannot change the original validity for unsupported combinations. |
| `200` | `MaturityMonthYear` | N   | Char         | Contract month in `YYYYMM` format when required by the symbol contract.                      |
| `167` | `SecurityType`      | N   | Char         | Security type when required. Use the value assigned for the session; `FUT` denotes futures.  |

## Replace response flow

| Step                                                                       | Response                                                                                                                 |
| -------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------ |
| Replace request is invalid                                                 | `OrderCancelReject (35=9)` with the current order status and rejection detail.                                           |
| Replace request contains no change in price or quantity                    | `OrderCancelReject (35=9)`.                                                                                              |
| Replace request attempts to change order type or validity when not allowed | `OrderCancelReject (35=9)`.                                                                                              |
| Replace request is accepted for processing                                 | `ExecutionReport (35=8)` with `OrdStatus (39)=E` and `ExecType (150)=E` for pending replace.                             |
| Replace succeeds                                                           | `ExecutionReport (35=8)` with `ExecType (150)=5` for replaced. `OrdStatus (39)` follows FIX 4.2 order-status precedence. |
| Replace fails after acceptance                                             | `OrderCancelReject (35=9)` with the current order status and rejection detail.                                           |

## Priority handling

| Amendment               | Priority behavior              |
| ----------------------- | ------------------------------ |
| Price changes           | Matching priority is reset.    |
| Quantity decreases only | Matching priority is retained. |
| Quantity increases      | Matching priority is reset.    |

## Validation notes

| Rule                     | Description                                                                                                        |
| ------------------------ | ------------------------------------------------------------------------------------------------------------------ |
| Original order reference | `OrigClOrdID (41)` must reference an order that can be cancelled or amended.                                       |
| One pending action       | A new cancel or replace request is rejected when the target order already has a pending cancel or replace request. |
| Immutable fields         | `Symbol (55)`, `Side (54)`, and the original order identity must remain unchanged.                                 |
| Completed orders         | Filled, cancelled, rejected, or expired orders cannot be cancelled or amended.                                     |
| Session restrictions     | Cancel and replace requests are permitted only in trading-session states that allow the action.                    |