diff --git a/ach/builder.py b/ach/builder.py
index 1a3c70f..89e17ac 100644
--- a/ach/builder.py
+++ b/ach/builder.py
@@ -94,6 +94,9 @@ def add_batch(self, std_ent_cls_code, batch_entries=None,
             entry.trace_num = self.settings['immediate_dest'][:8] \
                 + entry.validate_numeric_field(entry_counter, 7)
 
+            if 'id_number' in record:
+                entry.id_number = record['id_number'][:15]
+
             entries.append((entry, record.get('addenda', [])))
             entry_counter += 1
 
diff --git a/tests/test_line_endings.py b/tests/test_line_endings.py
index 6c8d075..facd029 100644
--- a/tests/test_line_endings.py
+++ b/tests/test_line_endings.py
@@ -41,6 +41,7 @@ def setup(self):
                 'account_number' : '123123123',
                 'amount'         : '12.13',
                 'name'           : 'Rachel Welch',
+                'id_number'      : '3333',
             },
         ]