diff --git a/moto/sqs/exceptions.py b/moto/sqs/exceptions.py
new file mode 100644
index 000000000..dd1d897b5
--- /dev/null
+++ b/moto/sqs/exceptions.py
@@ -0,0 +1,8 @@
+class MessageNotInflight(Exception):
+    description = "The message referred to is not in flight."
+    status_code = 400
+
+
+class ReceiptHandleIsInvalid(Exception):
+    description = "The receipt handle provided is not valid."
+    status_code = 400