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# OrderId

The Order ID is a client-managed identifier used to track, modify, and cancel orders. As a result, it must be strictly increasing.

The [`nextValidId()`](/tws-api/doc/next-valid-id/) callback function receives the next valid order ID. This function is called once upon initial connection.

The [`reqIds()`](/tws-api/doc/next-valid-id/request-next-valid-id) function can be used to request the next valid ID, which is returned via the [`nextValidId()`](/tws-api/doc/next-valid-id/) callback function.

```python title={"Python"}
class TestApp(EClient, EWrapper):
    def __init__(self):
        EClient.__init__(self, self)
        self.nextOrderId = None

    def nextValidId(self, orderId: OrderId):
        self.nextOrderId = orderId

```