# API VALIDATION ERROR CODES

All the validation error codes that can be [returned](api-response-format.md) by the API server.
In each case there may be more details in the `message` property where appropriate.

| CODE | MEANING |
| ----- | ------------------------------ |
| RequiredPropertyEmpty | Required property is missing or empty |
| LengthExceeded | A text property has more characters than are allowed.  The limit will be returned in the `message` property of the validation error |
| NotUnique | A text property is required to be unique but an existing identical value was found in the database |
| StartDateMustComeBeforeEndDate | When an object requires a start and end date the start date must be earlier than the end date |
| InvalidValue | Generic error indicating an input object's property is not set correctly |
| ReferentialIntegrity | Indicates modifying the object (usually a delete) will break the link to other records in the database.  The other records need to be modified before continuing |
| InvalidOperation | Indicates the operation is invalid, details provided in the `message`  |
| NotChangeable | Indicates the attempted property change is invalid because the value is fixed and cannot be changed  |
