diff --git a/tableauserverclient/models/group_item.py b/tableauserverclient/models/group_item.py
index 00f35e51..6dfce438 100644
--- a/tableauserverclient/models/group_item.py
+++ b/tableauserverclient/models/group_item.py
@@ -1,6 +1,7 @@
 from typing import Callable, Optional, TYPE_CHECKING
 
 from defusedxml.ElementTree import fromstring
+from typing_extensions import Self
 
 from .exceptions import UnpopulatedPropertyError
 from .property_decorators import property_not_empty, property_is_enum
@@ -157,3 +158,8 @@ def from_response(cls, resp, ns) -> list["GroupItem"]:
     @staticmethod
     def as_reference(id_: str) -> ResourceReference:
         return ResourceReference(id_, GroupItem.tag_name)
+
+    def to_reference(self: Self) -> ResourceReference:
+        if self.id is None:
+            raise ValueError("UserItem must have id to be converted to reference")
+        return ResourceReference(self.id, self.tag_name)
diff --git a/tableauserverclient/models/groupset_item.py b/tableauserverclient/models/groupset_item.py
index aa653a79..e586b266 100644
--- a/tableauserverclient/models/groupset_item.py
+++ b/tableauserverclient/models/groupset_item.py
@@ -2,6 +2,7 @@
 import xml.etree.ElementTree as ET
 
 from defusedxml.ElementTree import fromstring
+from typing_extensions import Self
 
 from tableauserverclient.models.group_item import GroupItem
 from tableauserverclient.models.reference_item import ResourceReference
@@ -51,3 +52,8 @@ def get_group(group_xml: ET.Element) -> GroupItem:
     @staticmethod
     def as_reference(id_: str) -> ResourceReference:
         return ResourceReference(id_, GroupSetItem.tag_name)
+
+    def to_reference(self: Self) -> ResourceReference:
+        if self.id is None:
+            raise ValueError("UserItem must have id to be converted to reference")
+        return ResourceReference(self.id, self.tag_name)
diff --git a/tableauserverclient/models/reference_item.py b/tableauserverclient/models/reference_item.py
index 4c1fff56..30536b4d 100644
--- a/tableauserverclient/models/reference_item.py
+++ b/tableauserverclient/models/reference_item.py
@@ -1,9 +1,12 @@
+from typing_extensions import Self
+
+
 class ResourceReference:
-    def __init__(self, id_, tag_name):
+    def __init__(self, id_: str | None, tag_name: str) -> None:
         self.id = id_
         self.tag_name = tag_name
 
-    def __str__(self):
+    def __str__(self) -> str:
         return f"<ResourceReference id={self._id} tag={self._tag_name}>"
 
     __repr__ = __str__
@@ -13,18 +16,21 @@ def __eq__(self, other: object) -> bool:
             return False
         return (self.id == other.id) and (self.tag_name == other.tag_name)
 
+    def __hash__(self: Self) -> int:
+        return hash((self.id, self.tag_name))
+
     @property
-    def id(self):
+    def id(self) -> str | None:
         return self._id
 
     @id.setter
-    def id(self, value):
+    def id(self, value: str | None) -> None:
         self._id = value
 
     @property
-    def tag_name(self):
+    def tag_name(self) -> str:
         return self._tag_name
 
     @tag_name.setter
-    def tag_name(self, value):
+    def tag_name(self, value: str) -> None:
         self._tag_name = value
diff --git a/tableauserverclient/models/user_item.py b/tableauserverclient/models/user_item.py
index 8b2dd3dd..04ccf9ef 100644
--- a/tableauserverclient/models/user_item.py
+++ b/tableauserverclient/models/user_item.py
@@ -5,6 +5,7 @@
 from typing import Optional, TYPE_CHECKING
 
 from defusedxml.ElementTree import fromstring
+from typing_extensions import Self
 
 from tableauserverclient.datetime_helpers import parse_datetime
 from tableauserverclient.models.site_item import SiteAuthConfiguration
@@ -377,6 +378,11 @@ def _parse_xml(cls, element_name, resp, ns):
     def as_reference(id_) -> ResourceReference:
         return ResourceReference(id_, UserItem.tag_name)
 
+    def to_reference(self: Self) -> ResourceReference:
+        if self.id is None:
+            raise ValueError("UserItem must have id to be converted to reference")
+        return ResourceReference(self.id, self.tag_name)
+
     @staticmethod
     def _parse_element(user_xml, ns):
         id = user_xml.get("id", None)
diff --git a/tableauserverclient/server/request_factory.py b/tableauserverclient/server/request_factory.py
index 877a18c3..8445008d 100644
--- a/tableauserverclient/server/request_factory.py
+++ b/tableauserverclient/server/request_factory.py
@@ -512,7 +512,10 @@ def add_req(self, rules: Iterable[PermissionsRule]) -> bytes:
         for rule in rules:
             grantee_capabilities_element = ET.SubElement(permissions_element, "granteeCapabilities")
             grantee_element = ET.SubElement(grantee_capabilities_element, rule.grantee.tag_name)
-            grantee_element.attrib["id"] = rule.grantee.id
+            if rule.grantee.id is not None:
+                grantee_element.attrib["id"] = rule.grantee.id
+            else:
+                raise ValueError("Grantee must have an ID")
 
             capabilities_element = ET.SubElement(grantee_capabilities_element, "capabilities")
             self._add_all_capabilities(capabilities_element, rule.capabilities)