diff --git a/jey_erp/custom_fields.py b/jey_erp/custom_fields.py
index 947ec0a..dbc1f85 100644
--- a/jey_erp/custom_fields.py
+++ b/jey_erp/custom_fields.py
@@ -552,7 +552,10 @@ def create_custom_fields():
                 fieldtype='Select',
                 options='\nAgricultural Products Act\nMetal Scrap Reception Act\nTire Products For Disposal Act\nPlastic Products For Disposal Act\nRawhide Supply\nOther Product Receipt Act',
                 insert_after='etaxes_agricultural_section',
-                description='Type of act for e-taxes'
+                description='Type of act for e-taxes',
+                # Shown and mandatory only for a Purchase Act.
+                depends_on='eval:doc.act_type == "Purchase Act"',
+                mandatory_depends_on='eval:doc.act_type == "Purchase Act"'
             ),
             dict(
                 fieldname='etaxes_purchase_id',