diff --git a/rattail/batch/custorder.py b/rattail/batch/custorder.py
index 861e0fb365ecb1393f2b9af0fe82651f470e0366..0f059eeb658bc3489186ae4860cba4c9a6e02c4b 100644
--- a/rattail/batch/custorder.py
+++ b/rattail/batch/custorder.py
@@ -458,6 +458,17 @@ class CustomerOrderBatchHandler(BatchHandler):
                                   "{}.custom_product_autocomplete() "
                                   "method.".format(__class__.__name__))
 
+    def why_not_add_product(self, product, batch):
+        """
+        This method can inspect the given product, and batch, to
+        determine if the product may be added to the batch as a new
+        row.  Useful to e.g. prevent one customer from ordering too
+        many things, etc.
+
+        :returns: If there is a reason not to add the product, should
+           return that reason as a string; otherwise ``None``.
+        """
+
     def refresh_row(self, row):
         if not row.product:
             if row.item_entry: