diff --git a/UPGRADE-4.0.md b/UPGRADE-4.0.md
new file mode 100644
index 000000000..66409565c
--- /dev/null
+++ b/UPGRADE-4.0.md
@@ -0,0 +1,8 @@
+# Upgrade 3.x to 4.0
+
+- The `send_attempts` option was removed. You may implement a custom transport if you rely on this behaviour.
+- `SpanContext::fromTraceparent()` was removed. Use `Sentry\continueTrace()` instead.
+- `TransactionContext::fromSentryTrace()` was removed. Use `Sentry\continueTrace()` instead.
+- The `IgnoreErrorsIntegration` integration was removed. Use the `ignore_errors` option instead.
+- `Sentry\Exception\InvalidArgumentException` was removed. Use `\InvalidArgumentException` instead.
+- `Sentry\Exception/ExceptionInterface` was removed.