diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 47e63c68..84a49088 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -101,7 +101,7 @@ Here are a few things you can do that will increase the likelihood of your pull
 
 ### Local development requirements
 
-* Python3.5+ installed.
+* Python3.8+ installed.
 
 ### Local installation
 
@@ -123,19 +123,22 @@ Here are a few things you can do that will increase the likelihood of your pull
 * We use [tox](https://tox.readthedocs.io/en/latest/) to create different python environments and execute tests.
 
 #### Local installation requirements
-* You need to have python interpreters for python 3.5, 3.6, 3.7, and 3.8 installed locally.
+* You need to have python interpreters for python 3.8, 3.9, 3.10, 3.11, 3.12, and 3.13 installed locally.
 * You can install them using [pyenv](https://github.com/pyenv/pyenv)
 * Install `pyenv` - follow https://github.com/pyenv/pyenv#installation
 * Install python versions required
     ```bash
-    pyenv install 3.5.9 && \
-    pyenv install 3.6.10 && \
-    pyenv install 3.7.6 && \
-    pyenv install 3.8.2
+    pyenv install 3.8 && \
+    pyenv install 3.9 && \
+    pyenv install 3.10 && \
+    pyenv install 3.11 && \
+    pyenv install 3.12 && \
+    pyenv install 3.13
     ```
+    Passing a `MAJOR.MINOR` prefix installs the latest patch release in that line.
 
 #### Running all tests
-* Activate pyenv installed python versions `pyenv local 3.5.9 3.6.10 3.7.6 3.8.2`
+* Activate pyenv installed python versions `pyenv local $(pyenv latest 3.8) $(pyenv latest 3.9) $(pyenv latest 3.10) $(pyenv latest 3.11) $(pyenv latest 3.12) $(pyenv latest 3.13)`
 * Activate virtual environment by running `source venv/bin/activate`
 * Execute `tox` to run all tests in all python versions
 
diff --git a/setup.cfg b/setup.cfg
index 89acffda..37cc7a8e 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,6 +1,3 @@
-[bdist_wheel]
-universal = 1
-
 [flake8]
 # Recommend matching the black line length (default 88),
 # rather than using the flake8 default of 79:
diff --git a/setup.py b/setup.py
index 4229c0da..a018b3e8 100644
--- a/setup.py
+++ b/setup.py
@@ -27,17 +27,21 @@ def read_file(filename):
 setup(
     author="Xero Developer API",
     author_email="api@xero.com",
-    python_requires=">=3.5",
+    python_requires=">=3.8",
     classifiers=[
         "Development Status :: 4 - Beta",
         "Intended Audience :: Developers",
         "License :: OSI Approved :: MIT License",
         "Natural Language :: English",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.5",
-        "Programming Language :: Python :: 3.6",
-        "Programming Language :: Python :: 3.7",
+        # Keep in step with the tox envlist, which is what exercises each of
+        # these interpreters. The CI workflow runs a subset of them.
         "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
+        "Programming Language :: Python :: 3.10",
+        "Programming Language :: Python :: 3.11",
+        "Programming Language :: Python :: 3.12",
+        "Programming Language :: Python :: 3.13",
     ],
     description="Official Python sdk for Xero API generated by OpenAPI spec for oAuth2",
     install_requires=load_requirements("requirements.txt"),
diff --git a/tox.ini b/tox.ini
index 4f2d367c..b4d4e261 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,12 +1,5 @@
 [tox]
-envlist = py35, py36, py37, py38, flake8
-
-;[travis]
-;python =
-;    3.8: py38
-;    3.7: py37
-;    3.6: py36
-;    3.5: py35
+envlist = py38, py39, py310, py311, py312, py313, flake8
 
 [testenv:flake8]
 basepython = python