diff --git a/CHANGELOG.md b/CHANGELOG.md
index adf69203..71d90b35 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 - Add support for `readOnly`.
 - Fix bug where TypedDIct types for `binary`, `date` and `date-time` string formats mapped to the incorrect python types.
+- Fix bug where `to_dict` and `to_str` returned `null` for values that are not required and not nullable.
 
 ## Version 1.1.0 - 2020-04-05
 
diff --git a/open_alchemy/utility_base/__init__.py b/open_alchemy/utility_base/__init__.py
index 70181b32..76846c7a 100644
--- a/open_alchemy/utility_base/__init__.py
+++ b/open_alchemy/utility_base/__init__.py
@@ -221,6 +221,15 @@ class UtilityBase:
         return_dict: typing.Dict[str, typing.Any] = {}
         for name, property_schema in properties.items():
             value = getattr(instance, name, None)
+
+            # Handle none value
+            if value is None:
+                return_none = to_dict.return_none(schema=schema, property_name=name)
+                if return_none is True:
+                    return_dict[name] = None
+                # Don't consider for coverage due to coverage bug
+                continue  # pragma: no cover
+
             try:
                 return_dict[name] = to_dict.convert(schema=property_schema, value=value)
             except exceptions.BaseError as exc:
diff --git a/open_alchemy/utility_base/to_dict/__init__.py b/open_alchemy/utility_base/to_dict/__init__.py
index 67079c56..41cd0680 100644
--- a/open_alchemy/utility_base/to_dict/__init__.py
+++ b/open_alchemy/utility_base/to_dict/__init__.py
@@ -31,3 +31,36 @@ def convert(*, schema: oa_types.Schema, value: typing.Any) -> types.TAnyDict:
     if type_ in {"integer", "number", "string", "boolean"}:
         return simple.convert(value, schema=schema)
     raise exceptions.FeatureNotImplementedError(f"Type {type_} is not supported.")
+
+
+def return_none(*, schema: oa_types.Schema, property_name: str) -> bool:
+    """
+    Check whether a null value for a property should be returned.
+
+    Assume the schema has properties and that it has a schema for the property.
+    Assume that any $ref and allOf has already been resolved.
+
+    The rules are:
+    1. if the property is required, return it,
+    2. if the property is nullable, return it and
+    3. else, don't return it.
+
+    Args:
+        schema: The schema for the model.
+        property_name: The name of the property to check for.
+
+    Returns:
+        Whether the none value should be returned for the property.
+
+    """
+    # Retrieve input
+    required_array = schema.get("required", None)
+    property_schema = schema["properties"][property_name]
+
+    # Check for required and nullable
+    if required_array is not None and property_name in set(required_array):
+        return True
+    nullable_value = helpers.peek.nullable(schema=property_schema, schemas={})
+    if nullable_value is True:
+        return True
+    return False

Don't return null column values unless they are required for to_dict and to_str
`null` values for non-required properties are not valid JSON schema dictionaries unless they are nullable. Change the rule for null values to:

- [ ] If the value is required, return it.
- [ ] If the value is nullable, return it.
- [ ] If the value is not nullable and not required, don't return it.
diff --git a/tests/open_alchemy/utility_base/test_to_dict.py b/tests/open_alchemy/utility_base/test_to_dict.py
index eba6f58c..51713a44 100644
--- a/tests/open_alchemy/utility_base/test_to_dict.py
+++ b/tests/open_alchemy/utility_base/test_to_dict.py
@@ -41,14 +41,31 @@ def test_to_dict_no_properties(__init__):
 @pytest.mark.parametrize(
     "schema, value, expected_value",
     [
-        ({"properties": {"key": {"type": "integer"}}}, {"key": 1}, {"key": 1}),
-        (
+        pytest.param(
+            {"properties": {"key": {"type": "integer"}}},
+            {"key": 1},
+            {"key": 1},
+            id="single",
+        ),
+        pytest.param(
+            {"properties": {"key": {"type": "integer"}}},
+            {"key": None},
+            {},
+            id="single null value not return",
+        ),
+        pytest.param(
+            {"properties": {"key": {"type": "integer", "nullable": True}}},
+            {"key": None},
+            {"key": None},
+            id="single null value return",
+        ),
+        pytest.param(
             {"properties": {"key_1": {"type": "integer"}, "key_2": {"type": "string"}}},
             {"key_1": 1, "key_2": "value 2"},
             {"key_1": 1, "key_2": "value 2"},
+            id="multiple",
         ),
     ],
-    ids=["single", "multiple"],
 )
 @pytest.mark.utility_base
 def test_valid(__init__, schema, value, expected_value):
diff --git a/tests/open_alchemy/utility_base/to_dict/test_to_dict.py b/tests/open_alchemy/utility_base/to_dict/test_to_dict.py
new file mode 100644
index 00000000..fe056fd8
--- /dev/null
+++ b/tests/open_alchemy/utility_base/to_dict/test_to_dict.py
@@ -0,0 +1,74 @@
+"""Tests for to_dict."""
+
+import pytest
+
+from open_alchemy.utility_base import to_dict
+
+
+@pytest.mark.parametrize(
+    "schema, expected_result",
+    [
+        pytest.param(
+            {"properties": {"prop_1": {"key": "value"}}},
+            False,
+            id="nullable not set required not set expect false",
+        ),
+        pytest.param(
+            {"properties": {"prop_1": {"key": "value"}}, "required": []},
+            False,
+            id="nullable not set required empty expect false",
+        ),
+        pytest.param(
+            {"properties": {"prop_1": {"key": "value"}}, "required": ["prop_2"]},
+            False,
+            id="nullable not set required different property expect false",
+        ),
+        pytest.param(
+            {"properties": {"prop_1": {"key": "value"}}, "required": ["prop_1"]},
+            True,
+            id="nullable not set required has property expect true",
+        ),
+        pytest.param(
+            {
+                "properties": {"prop_1": {"key": "value", "nullable": False}},
+                "required": [],
+            },
+            False,
+            id="nullable false required empty expect false",
+        ),
+        pytest.param(
+            {
+                "properties": {"prop_1": {"key": "value", "nullable": False}},
+                "required": ["prop_1"],
+            },
+            True,
+            id="nullable false required has property expect true",
+        ),
+        pytest.param(
+            {
+                "properties": {"prop_1": {"key": "value", "nullable": True}},
+                "required": [],
+            },
+            True,
+            id="nullable true required empty expect true",
+        ),
+        pytest.param(
+            {
+                "properties": {"prop_1": {"key": "value", "nullable": True}},
+                "required": ["prop_1"],
+            },
+            True,
+            id="nullable true required has property expect true",
+        ),
+    ],
+)
+@pytest.mark.utility_base
+def test_return_none(schema, expected_result):
+    """
+    GIVEN schema with property and expected result
+    WHEN return_none is called with the schema and property name
+    THEN the expected result is returned.
+    """
+    result = to_dict.return_none(schema=schema, property_name="prop_1")
+
+    assert result == expected_result

pip install -e .[dev,test]
parse_log_pytest
pytest
pytest pytest-cov pytest-flake8 pytest-flask pytest-flask-sqlalchemy pytest-randomly pytest-bandit typeguard
apt-get update apt-get install -y gcc
3.8
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
alabaster==0.7.13
alembic==1.14.1
anyio==4.5.2
asgiref==3.8.1
astroid==3.2.4
attrs==25.3.0
babel==2.17.0
bandit==1.7.10
black==24.8.0
blinker==1.8.2
cachetools==5.5.2
certifi==2025.1.31
cfgv==3.4.0
chardet==5.2.0
charset-normalizer==3.4.1
click==8.1.8
colorama==0.4.6
connexion==3.2.0
coverage==7.6.1
dill==0.3.9
distlib==0.3.9
doc8==1.1.2
docutils==0.20.1
exceptiongroup @ file:///croot/exceptiongroup_1706031385326/work
filelock==3.16.1
flake8==5.0.4
Flask==3.0.3
Flask-SQLAlchemy==3.1.1
greenlet==3.1.1
h11==0.14.0
httpcore==1.0.7
httpx==0.28.1
identify==2.6.1
idna==3.10
imagesize==1.4.1
importlib-resources==5.13.0
importlib_metadata==8.5.0
inflection==0.5.1
iniconfig @ file:///home/linux1/recipes/ci/iniconfig_1610983019677/work
isort==5.13.2
itsdangerous==2.2.0
Jinja2==3.1.6
jsonschema==4.23.0
jsonschema-specifications==2023.12.1
Mako==1.3.9
markdown-it-py==3.0.0
MarkupSafe==2.1.5
mccabe==0.7.0
mdurl==0.1.2
mypy==1.14.1
mypy-extensions==1.0.0
nodeenv==1.9.1
-e git+https://github.com/jdkandersson/OpenAlchemy.git@30d50467bb784b87f98e9464f127012c9679d5b5#egg=OpenAlchemy
packaging==24.2
pathspec==0.12.1
pbr==6.1.1
pkgutil_resolve_name==1.3.10
platformdirs==4.3.6
pluggy==1.5.0
pre-commit==3.5.0
pycodestyle==2.9.1
pydocstyle==6.3.0
pyflakes==2.5.0
Pygments==2.19.1
pylint==3.2.7
pyproject-api==1.8.0
pytest @ file:///croot/pytest_1717793244625/work
pytest-bandit==0.6.1
pytest-cov==5.0.0
pytest-flake8==1.2.2
pytest-flask==1.3.0
pytest-flask-sqlalchemy==1.1.0
pytest-mock==3.14.0
pytest-randomly==3.15.0
python-multipart==0.0.20
pytz==2025.2
PyYAML==6.0.2
referencing==0.35.1
requests==2.32.3
restructuredtext_lint==1.4.0
rich==14.0.0
rpds-py==0.20.1
sniffio==1.3.1
snowballstemmer==2.2.0
Sphinx==7.1.2
sphinxcontrib-applehelp==1.0.4
sphinxcontrib-devhelp==1.0.2
sphinxcontrib-htmlhelp==2.0.1
sphinxcontrib-jsmath==1.0.1
sphinxcontrib-qthelp==1.0.3
sphinxcontrib-serializinghtml==1.1.5
SQLAlchemy==2.0.40
starlette==0.44.0
stevedore==5.3.0
swagger_ui_bundle==1.1.0
tomli==2.2.1
tomlkit==0.13.2
tox==4.25.0
tox-pyenv==1.1.0
typeguard==4.4.0
typing_extensions==4.13.0
urllib3==2.2.3
virtualenv==20.29.3
Werkzeug==3.0.6
zipp==3.20.2

name: OpenAlchemy
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - exceptiongroup=1.2.0=py38h06a4308_0
  - iniconfig=1.1.1=pyhd3eb1b0_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.4.4=h6a678d5_1
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=3.0.16=h5eee18b_0
  - pip=24.2=py38h06a4308_0
  - pytest=7.4.4=py38h06a4308_0
  - python=3.8.20=he870216_0
  - readline=8.2=h5eee18b_0
  - setuptools=75.1.0=py38h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.44.0=py38h06a4308_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - alabaster==0.7.13
      - alembic==1.14.1
      - anyio==4.5.2
      - asgiref==3.8.1
      - astroid==3.2.4
      - attrs==25.3.0
      - babel==2.17.0
      - bandit==1.7.10
      - black==24.8.0
      - blinker==1.8.2
      - cachetools==5.5.2
      - certifi==2025.1.31
      - cfgv==3.4.0
      - chardet==5.2.0
      - charset-normalizer==3.4.1
      - click==8.1.8
      - colorama==0.4.6
      - connexion==3.2.0
      - coverage==7.6.1
      - dill==0.3.9
      - distlib==0.3.9
      - doc8==1.1.2
      - docutils==0.20.1
      - filelock==3.16.1
      - flake8==5.0.4
      - flask==3.0.3
      - flask-sqlalchemy==3.1.1
      - greenlet==3.1.1
      - h11==0.14.0
      - httpcore==1.0.7
      - httpx==0.28.1
      - identify==2.6.1
      - idna==3.10
      - imagesize==1.4.1
      - importlib-metadata==8.5.0
      - importlib-resources==5.13.0
      - inflection==0.5.1
      - isort==5.13.2
      - itsdangerous==2.2.0
      - jinja2==3.1.6
      - jsonschema==4.23.0
      - jsonschema-specifications==2023.12.1
      - mako==1.3.9
      - markdown-it-py==3.0.0
      - markupsafe==2.1.5
      - mccabe==0.7.0
      - mdurl==0.1.2
      - mypy==1.14.1
      - mypy-extensions==1.0.0
      - nodeenv==1.9.1
      - packaging==24.2
      - pathspec==0.12.1
      - pbr==6.1.1
      - pkgutil-resolve-name==1.3.10
      - platformdirs==4.3.6
      - pluggy==1.5.0
      - pre-commit==3.5.0
      - pycodestyle==2.9.1
      - pydocstyle==6.3.0
      - pyflakes==2.5.0
      - pygments==2.19.1
      - pylint==3.2.7
      - pyproject-api==1.8.0
      - pytest-bandit==0.6.1
      - pytest-cov==5.0.0
      - pytest-flake8==1.2.2
      - pytest-flask==1.3.0
      - pytest-flask-sqlalchemy==1.1.0
      - pytest-mock==3.14.0
      - pytest-randomly==3.15.0
      - python-multipart==0.0.20
      - pytz==2025.2
      - pyyaml==6.0.2
      - referencing==0.35.1
      - requests==2.32.3
      - restructuredtext-lint==1.4.0
      - rich==14.0.0
      - rpds-py==0.20.1
      - sniffio==1.3.1
      - snowballstemmer==2.2.0
      - sphinx==7.1.2
      - sphinxcontrib-applehelp==1.0.4
      - sphinxcontrib-devhelp==1.0.2
      - sphinxcontrib-htmlhelp==2.0.1
      - sphinxcontrib-jsmath==1.0.1
      - sphinxcontrib-qthelp==1.0.3
      - sphinxcontrib-serializinghtml==1.1.5
      - sqlalchemy==2.0.40
      - starlette==0.44.0
      - stevedore==5.3.0
      - swagger-ui-bundle==1.1.0
      - tomli==2.2.1
      - tomlkit==0.13.2
      - tox==4.25.0
      - tox-pyenv==1.1.0
      - typeguard==4.4.0
      - typing-extensions==4.13.0
      - urllib3==2.2.3
      - virtualenv==20.29.3
      - werkzeug==3.0.6
      - zipp==3.20.2
prefix: /opt/conda/envs/OpenAlchemy

tests/open_alchemy/utility_base/to_dict/test_to_dict.py::test_return_none[nullable tests/open_alchemy/utility_base/test_to_dict.py::test_valid[single
tests/open_alchemy/utility_base/test_to_dict.py::flake-8::FLAKE8 tests/open_alchemy/utility_base/to_dict/test_to_dict.py::flake-8::FLAKE8 tests/open_alchemy/utility_base/test_to_dict.py::test_to_dict_no_properties tests/open_alchemy/utility_base/test_to_dict.py::test_to_dict_inheritance_call tests/open_alchemy/utility_base/test_to_dict.py::test_valid[single] tests/open_alchemy/utility_base/test_to_dict.py::test_valid[multiple] tests/open_alchemy/utility_base/test_to_dict.py::test_to_dict_backrefs_object tests/open_alchemy/utility_base/test_to_dict.py::test_to_dict_error tests/open_alchemy/utility_base/test_to_dict.py::test_to_str tests/open_alchemy/utility_base/test_to_dict.py::test_to_dict_no_schema
open_alchemy/utility_base/to_dict/__init__.py CHANGELOG.md open_alchemy/utility_base/__init__.py
open_alchemy/utility_base/to_dict/__init__.py CHANGELOG.md open_alchemy/utility_base/__init__.py