diff --git a/scim2_models/base.py b/scim2_models/base.py
index d427673..396bd47 100644
--- a/scim2_models/base.py
+++ b/scim2_models/base.py
@@ -1,6 +1,7 @@
 import warnings
 from inspect import isclass
 from typing import Any
+from typing import ClassVar
 from typing import Optional
 from typing import get_args
 from typing import get_origin
@@ -112,6 +113,14 @@ class BaseModel(PydanticBaseModel):
         extra="forbid",
     )
 
+    _allow_bulk_id: ClassVar[bool] = False
+    """Allow bulkId field for the model"""
+
+    @classmethod
+    def __pydantic_init_subclass__(cls, **kwargs: Any) -> None:
+        # Validate field names
+        cls._check_bulk_id()
+
     @classmethod
     def get_field_annotation(cls, field_name: str, annotation_type: type) -> Any:
         """Return the annotation of type 'annotation_type' of the field 'field_name'.
@@ -538,6 +547,19 @@ def _set_complex_attribute_urns(self) -> None:
                 else:
                     attr_value._attribute_urn = schema
 
+    @classmethod
+    def _check_bulk_id(cls) -> None:
+        """Enforce bulkId as reserved field per RFC 7643 §3.1.
+
+        Check if a bulkdId field is defined and
+        raise error if `_allow_bulk_id` is set to `False`
+        """
+        if cls._allow_bulk_id:
+            return
+        for info in cls.model_fields.values():
+            if info.serialization_alias == "bulkId":
+                raise TypeError(f"{cls.__name__}: bulkId is reserved for BulkOperation")
+
     @field_serializer("*", mode="wrap")
     def scim_serializer(
         self,
diff --git a/scim2_models/messages/bulk.py b/scim2_models/messages/bulk.py
index 7c2f19f..1468ba4 100644
--- a/scim2_models/messages/bulk.py
+++ b/scim2_models/messages/bulk.py
@@ -12,6 +12,8 @@
 
 
 class BulkOperation(ComplexAttribute):
+    _allow_bulk_id = True
+
     class Method(str, Enum):
         post = "POST"
         put = "PUT"
diff --git a/tests/test_model_attributes.py b/tests/test_model_attributes.py
index 418b88c..428bfa9 100644
--- a/tests/test_model_attributes.py
+++ b/tests/test_model_attributes.py
@@ -1,6 +1,8 @@
 import uuid
 from typing import Annotated
 
+import pytest
+
 from scim2_models import URN
 from scim2_models.annotations import Returned
 from scim2_models.attributes import ComplexAttribute
@@ -377,3 +379,14 @@ def test_short_attr_path_with_plain_name():
 
     assert _short_attr_path("userName") == "userName"
     assert _short_attr_path("name.familyName") == "name.familyName"
+
+
+def test_forbid_bulk_id():
+    """Forbid bulkId from class definition."""
+    with pytest.raises(TypeError) as exc_info:
+
+        class CustomModel(Resource):
+            __schema__ = URN("urn:example:schemas:CustomModel")
+            bulk_id: str | None = None
+
+    assert str(exc_info.value) == "CustomModel: bulkId is reserved for BulkOperation"