diff --git a/nhs_number/generate.py b/nhs_number/generate.py
index a919ea9..572bd6e 100644
--- a/nhs_number/generate.py
+++ b/nhs_number/generate.py
@@ -23,7 +23,6 @@ def generate(
     for_region: Region = None,
     quantity: int = 1,
 ) -> list:
-
     """
     Generates valid or invalid NHS numbers, for testing.
 
diff --git a/nhs_number/standardise.py b/nhs_number/standardise.py
index fba12f6..dbcd6ab 100644
--- a/nhs_number/standardise.py
+++ b/nhs_number/standardise.py
@@ -10,7 +10,9 @@
 * Marcus Baw <marcusbaw@gmail.com>
 """
 # standard imports
-from __future__ import annotations # for Python 3.7 (remove once we stop supporting 3.7)
+from __future__ import (
+    annotations,
+)  # for Python 3.7 (remove once we stop supporting 3.7)
 import re
 import warnings
 
@@ -51,6 +53,11 @@ def standardise_format(nhs_number: str | int) -> str:
 
 
 def normalise_number(nhs_number: str) -> str:
-    warnings.warn("The normalise_number() function is deprecated - use "
-                  "standardise_format() instead", DeprecationWarning)
+    warnings.warn(
+        (
+            "The normalise_number() function is deprecated - use "
+            "standardise_format() instead"
+        ),
+        DeprecationWarning,
+    )
     return standardise_format(nhs_number)
diff --git a/nhs_number/validate.py b/nhs_number/validate.py
index f5089d2..a0021bc 100644
--- a/nhs_number/validate.py
+++ b/nhs_number/validate.py
@@ -9,7 +9,9 @@
 * Andy Law <andy.law@roslin.ed.ac.uk>
 * Marcus Baw <marcusbaw@gmail.com>
 """
-from __future__ import annotations # for Python 3.7 (remove once we stop supporting 3.7)
+from __future__ import (
+    annotations,
+)  # for Python 3.7 (remove once we stop supporting 3.7)
 from nhs_number.standardise import standardise_format
 from nhs_number.constants import Region
 
diff --git a/pyproject.toml b/pyproject.toml
index fe6dc65..9dc0247 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -38,11 +38,13 @@ python = "^3.7"
 pytest = "^7.3.1"
 black = "^23.3.0"
 mkdocs-material = "^9.1.15"
+tox = "^4.8.0"
 
 
 [tool.poetry.urls]
 "Issue Tracker" = "https://github.com/uk-fci/nhs-number/issues"
 
+
 [build-system]
 requires = ["poetry-core"]
 build-backend = "poetry.core.masonry.api"
diff --git a/tests/context.py b/tests/context.py
index e4d94cf..7973942 100644
--- a/tests/context.py
+++ b/tests/context.py
@@ -1,6 +1,8 @@
 import os
 import sys
 
-sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..")))
+sys.path.insert(
+    0, os.path.abspath(os.path.join(os.path.dirname(__file__), ".."))
+)
 
 import nhs_number
diff --git a/tests/test_bulk_validation.py b/tests/test_bulk_validation.py
index aab20fd..079e011 100644
--- a/tests/test_bulk_validation.py
+++ b/tests/test_bulk_validation.py
@@ -17,10 +17,14 @@
 
 
 @pytest.mark.skipif(
-    not os.path.exists("local-test-data/testdata-909090-valid-nhs-numbers.csv"),
-    reason="This test requires a large list of valid NHS numbers which we do"
-           " not want to include in the repo by default for reasons of file"
-           " size",
+    not os.path.exists(
+        "local-test-data/testdata-909090-valid-nhs-numbers.csv"
+    ),
+    reason=(
+        "This test requires a large list of valid NHS numbers which we do"
+        " not want to include in the repo by default for reasons of file"
+        " size"
+    ),
 )
 def test_with_large_numbers_of_known_valid_nhs_numbers():
     with open(
diff --git a/tests/test_details.py b/tests/test_details.py
index 01860d7..48b51c2 100644
--- a/tests/test_details.py
+++ b/tests/test_details.py
@@ -12,5 +12,7 @@ def test_valid_synthetic_nhs_number_details():
     assert number.calculated_checksum == 0
     assert isinstance(number.region, Region)
     assert "test" in number.region.tags
-    assert number.region_comment == ("Not to be issued "
-                                     "(Synthetic/test patients PDS)")
+    assert (
+        number.region_comment
+        == "Not to be issued (Synthetic/test patients PDS)"
+    )
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..d594819
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,14 @@
+[tox]
+isolated_build = true
+envlist = black, py{37,38,39,310,311}
+
+[testenv]
+allowlist_externals = poetry
+commands =
+    poetry install -v
+    poetry run pytest --ignore=tests/test_bulk_validation.py
+
+[testenv:black]
+description = 'Check code format with Black'
+commands = poetry run black --check .
+