diff --git a/invoice_az/hooks.py b/invoice_az/hooks.py
index 8761efa..7af745f 100644
--- a/invoice_az/hooks.py
+++ b/invoice_az/hooks.py
@@ -73,18 +73,22 @@ def after_install():
 	"""Run installation tasks"""
 	from invoice_az.auth import setup_token_renewal
 	from invoice_az.master_data.sync import sync_all
+	from invoice_az.setup_defaults import ensure_settings_defaults
 
 	setup_token_renewal()
 	sync_all()
+	ensure_settings_defaults()
 
 
 def after_migrate():
 	"""Run migration tasks"""
 	from invoice_az.auth import setup_token_renewal
 	from invoice_az.master_data.sync import sync_all
+	from invoice_az.setup_defaults import ensure_settings_defaults
 
 	setup_token_renewal()
 	sync_all()
+	ensure_settings_defaults()
 
 
 fixtures = []
diff --git a/invoice_az/setup_defaults.py b/invoice_az/setup_defaults.py
new file mode 100644
index 0000000..d7dbf00
--- /dev/null
+++ b/invoice_az/setup_defaults.py
@@ -0,0 +1,33 @@
+import frappe
+
+# Sensible out-of-the-box defaults for E-Taxes Settings on a fresh base.
+# These are required Link fields with no field-level default, so without this
+# they start empty on every new install and have to be filled by hand.
+SETTINGS_DEFAULTS = {
+    "default_item_group": ("Item Group", "All Item Groups"),
+    "default_uom": ("UOM", "Nos"),
+}
+
+
+def ensure_settings_defaults():
+    """Populate E-Taxes Settings defaults if they are empty.
+
+    Idempotent: only writes a field when it is currently blank AND the target
+    record exists. Safe to run on every after_install / after_migrate — it
+    never overwrites a value an admin has already chosen.
+    """
+    settings = frappe.get_single("E-Taxes Settings")
+
+    changed = False
+    for fieldname, (doctype, value) in SETTINGS_DEFAULTS.items():
+        if settings.get(fieldname):
+            continue
+        if not frappe.db.exists(doctype, value):
+            continue
+        settings.set(fieldname, value)
+        changed = True
+
+    if changed:
+        settings.flags.ignore_permissions = True
+        settings.save(ignore_permissions=True)
+        frappe.db.commit()