diff --git a/fusion_plating/fusion_plating_configurator/tests/test_charge_tax_lot.py b/fusion_plating/fusion_plating_configurator/tests/test_charge_tax_lot.py
index 3909c110..38a06ddd 100644
--- a/fusion_plating/fusion_plating_configurator/tests/test_charge_tax_lot.py
+++ b/fusion_plating/fusion_plating_configurator/tests/test_charge_tax_lot.py
@@ -28,3 +28,19 @@ class TestChargeTaxLot(TransactionCase):
         self.assertEqual(ct.default_amount, 75.0)
         cid, cname = self.env['fp.additional.charge.type'].name_create('Setup')
         self.assertTrue(cid)
+
+    # ----- Task 3: totals -----
+    def _make_wizard(self, **kw):
+        vals = {'partner_id': self.partner.id}
+        vals.update(kw)
+        return self.env['fp.direct.order.wizard'].create(vals)
+
+    def test_tax_applies_on_subtotal_plus_charge(self):
+        wiz = self._make_wizard(charge_amount=100.0, tax_id=self.tax13.id)
+        self.env['fp.direct.order.line'].create({
+            'wizard_id': wiz.id, 'quantity': 1, 'unit_price': 50.0,
+        })
+        wiz.invalidate_recordset()
+        self.assertEqual(wiz.total_subtotal, 50.0)
+        self.assertAlmostEqual(wiz.total_tax, 19.5, places=2)
+        self.assertAlmostEqual(wiz.total_amount, 169.5, places=2)
diff --git a/fusion_plating/fusion_plating_configurator/wizard/fp_direct_order_wizard.py b/fusion_plating/fusion_plating_configurator/wizard/fp_direct_order_wizard.py
index 062cb8bf..bef86e7a 100644
--- a/fusion_plating/fusion_plating_configurator/wizard/fp_direct_order_wizard.py
+++ b/fusion_plating/fusion_plating_configurator/wizard/fp_direct_order_wizard.py
@@ -401,65 +401,41 @@ class FpDirectOrderWizard(models.Model):
 
     # ---- Computes ----
     @api.depends(
-        'line_ids.line_subtotal',
         'line_ids.quantity',
         'line_ids.unit_price',
-        'line_ids.tax_ids',
+        'charge_amount',
         'tooling_charge',
+        'tax_id',
         'partner_id',
         'currency_id',
     )
     def _compute_totals(self):
-        """Roll up subtotal / tax / grand total across lines + tooling.
+        """Roll up subtotal / tax / grand total across lines + charge.
 
-        Each line's taxes are computed via account.tax.compute_all so the
-        Express form's totals card mirrors what the eventual SO will show
-        once the operator hits Confirm. The tooling charge is added at the
-        wizard level here AND pushed as an actual sale.order.line at
-        action_create_order time (so it carries into the invoice).
+        The order-level ``tax_id`` is applied once to (subtotal + charge),
+        where charge = ``charge_amount`` (legacy ``tooling_charge`` as
+        fallback). The charge is also pushed as an actual sale.order.line
+        at action_create_order time (so it carries into the invoice).
         """
         for rec in self:
-            subtotal = 0.0
+            subtotal = sum(
+                (l.quantity or 0) * (l.unit_price or 0.0)
+                for l in rec.line_ids
+            )
+            charge = rec.charge_amount or rec.tooling_charge or 0.0
             tax_total = 0.0
-            for line in rec.line_ids:
-                line_pre_tax = (line.quantity or 0) * (line.unit_price or 0.0)
-                subtotal += line_pre_tax
-                if line.tax_ids and line_pre_tax:
-                    taxes_res = line.tax_ids.compute_all(
-                        line.unit_price or 0.0,
-                        currency=rec.currency_id,
-                        quantity=line.quantity or 0,
-                        product=None,
-                        partner=rec.partner_id or None,
-                    )
-                    tax_total += (
-                        taxes_res['total_included']
-                        - taxes_res['total_excluded']
-                    )
-            # Tooling charge: pick the tax set from the FIRST line that
-            # has one (best proxy for the customer's standard rate). If
-            # no line has taxes set yet, tooling is shown untaxed in the
-            # preview; the eventual SO line will apply product defaults.
-            tooling = rec.tooling_charge or 0.0
-            if tooling:
-                first_taxed_line = next(
-                    (l for l in rec.line_ids if l.tax_ids), False,
+            if rec.tax_id and (subtotal + charge):
+                res = rec.tax_id.compute_all(
+                    subtotal + charge,
+                    currency=rec.currency_id,
+                    quantity=1,
+                    product=None,
+                    partner=rec.partner_id or None,
                 )
-                if first_taxed_line:
-                    tooling_res = first_taxed_line.tax_ids.compute_all(
-                        tooling,
-                        currency=rec.currency_id,
-                        quantity=1,
-                        product=None,
-                        partner=rec.partner_id or None,
-                    )
-                    tax_total += (
-                        tooling_res['total_included']
-                        - tooling_res['total_excluded']
-                    )
+                tax_total = res['total_included'] - res['total_excluded']
             rec.total_subtotal = subtotal
             rec.total_tax = tax_total
-            rec.total_amount = subtotal + tax_total + tooling
+            rec.total_amount = subtotal + charge + tax_total
             rec.total_qty = sum(rec.line_ids.mapped('quantity'))
             rec.total_line_count = len(rec.line_ids)