diff --git a/api-ref/source/errors.inc b/api-ref/source/errors.inc
new file mode 100644
index 000000000..4419162c0
--- /dev/null
+++ b/api-ref/source/errors.inc
@@ -0,0 +1,69 @@
+======
+Errors
+======
+
+When there is an error interacting with the placement API, the response will
+include a few different signals of what went wrong, include the status header
+and information in the response body. The structure of the ``JSON`` body of an
+error response is defined by the OpenStack errors_ guideline.
+
+**HTTP Status Code**
+    The ``Status`` header of the response will include a code, defined by
+    :rfc:`7231#section-6` that gives a general overview of the problem.
+    This value also shows up in a ``status`` attribute in the body of the
+    response.
+
+**Detail Message**
+    A textual description of the error condition, in a ``detail`` attribute.
+    The value is usually the message associated with whatever exception
+    happened within the service.
+
+**Error Code**
+    When the microversion is ``>=1.23`` responses will also include a ``code``
+    attribute in the ``JSON`` body. These are documented below. Where a
+    response does not use a specific code ``placement.undefined_code`` is
+    present.
+
+.. note:: In some cases, for example when keystone is being used and no
+          authentication information is provided in a request (causing a
+          ``401`` response), the structure of the error response will not match
+          the above because the error is produced by code other than the
+          placement service.
+
+
+Error Codes
+===========
+
+The defined errors are:
+
+.. list-table::
+   :header-rows: 1
+
+   * - Code
+     - Meaning
+   * - ``placement.undefined_code``
+     - The default code used when a specific code has not been defined or is
+       not required.
+   * - ``placement.inventory.inuse``
+     - An attempt has been made to remove or shrink inventory that has capacity
+       in use.
+   * - ``placement.concurrent_update``
+     - Another operation has concurrently made a request that involves one or
+       more of the same resources referenced in this request, changing state.
+       The current state should be retrieved to determine if the desired
+       operation should be retried.
+   * - ``placement.duplicate_name``
+     - A resource of this type already exists with the same name, and duplicate
+       names are not allowed.
+   * - ``placement.resource_provider.inuse``
+     - An attempt was made to remove a resource provider, but there are
+       allocations against its inventory.
+   * - ``placement.resource_provider.cannot_delete_parent``
+     - An attempt was made to remove a resource provider, but it has one or
+       more child providers. They must be removed first in order to remove this
+       provider.
+   * - ``placement.resource_provider.not_found``
+     - A resource provider mentioned in an operation involving multiple
+       resource providers, such as :ref:`reshaper`, does not exist.
+
+.. _errors: https://specs.openstack.org/openstack/api-wg/guidelines/errors.html
diff --git a/api-ref/source/index.rst b/api-ref/source/index.rst
index 30c900195..c356454ed 100644
--- a/api-ref/source/index.rst
+++ b/api-ref/source/index.rst
@@ -15,6 +15,7 @@ header for APIs sending data payloads in the request body (i.e. ``PUT`` and
 .. rest_expand_all::
 
 .. include:: request-ids.inc
+.. include:: errors.inc
 .. include:: root.inc
 .. include:: resource_providers.inc
 .. include:: resource_provider.inc
diff --git a/api-ref/source/reshaper.inc b/api-ref/source/reshaper.inc
index ee68bce03..4d23a8913 100644
--- a/api-ref/source/reshaper.inc
+++ b/api-ref/source/reshaper.inc
@@ -1,3 +1,6 @@
+
+.. _reshaper:
+
 ========
 Reshaper
 ========
diff --git a/doc/source/contributor/index.rst b/doc/source/contributor/index.rst
index 0979291db..817d93168 100644
--- a/doc/source/contributor/index.rst
+++ b/doc/source/contributor/index.rst
@@ -157,6 +157,8 @@ the code:
   ``placement/tests/functional/gabbits/microversion.yaml``.
 * Update the `API Reference`_ documentation as appropriate.  The source is
   located under ``api-ref/source/``.
+* If a new error code has been added in ``placement/errors.py``, it should
+  be added to the `API Reference`_.
 
 In the placement API, microversions only use the modern form of the
 version header::
@@ -265,7 +267,8 @@ by using the ``comment`` kwarg to a WebOb exception, like this::
             comment=errors.INVENTORY_INUSE)
 
 Code that adds newly raised exceptions should include an error code. Find
-additional guidelines on use in the docs for ``placement.errors``.
+additional guidelines on use in the docs for ``placement.errors``. When a
+new error code is added, also document it in the `API Reference`_.
 
 Testing of handler code is described in the next section.