diff --git a/documents/bierbook/2025/readme.txt b/documents/bierbook/2025/readme.txt
new file mode 100644
index 000000000..619c98f3b
--- /dev/null
+++ b/documents/bierbook/2025/readme.txt
@@ -0,0 +1,5 @@
+The file 
+<year>/names.txt
+is overwritten automatically by the online signup form 
+expo.survex.com/signup
+with the names of all the people currently signed up.
\ No newline at end of file