diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 4c5eabb..54d6cfb 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -15,3 +15,28 @@ Make sure to wait a few days to let others comment on your changes.
 
 4. If there are no objections and you've resolved any issues that might have been brought up, rebase the commits onto the `master` branch.
 If there are many commits, consider 'squashing' them into one with a single meaningful message when rebasing.
+
+## Licensing and copyright
+
+`matchbot` is open source software, allowing anyone to use it without restriction.
+In order to maintain this, please take the time to ensure that your contributions are properly licensed.
+
+### Developer Certificate of Origin
+
+Please include a '`Signed-off-by:`' line in the message of each commit to show that you have agreed to the [Developer Certificate of Origin, version 1.1](https://developercertificate.org/).
+You can add this automatically by using the `--signoff` flag when running `git commit`.
+
+### REUSE headers
+
+`matchbot` follows the [REUSE specification](https://reuse.software/) to make it easy for people to find out its licensing and copyright.
+
+As such, all files should start with a comment of the file's licence:
+
+> `;; SPDX-License-Identifier: Apache-2.0`
+
+When you modify a file, add a copyright header comment to it with the year when you first modified the file, your name and finally your email address.
+For example:
+
+> `;; SPDX-FileCopyrightText: 2022 Joe Bloggs <joe@example.com>`
+
+If the copyright to your contributions is held by your employer, put your employer's name in brackets after your own name.