diff --git a/fusion_plating/docs/superpowers/specs/2026-05-29-manager-invoice-permission-design.md b/fusion_plating/docs/superpowers/specs/2026-05-29-manager-invoice-permission-design.md
new file mode 100644
index 00000000..7c0b2bc3
--- /dev/null
+++ b/fusion_plating/docs/superpowers/specs/2026-05-29-manager-invoice-permission-design.md
@@ -0,0 +1,71 @@
+# Managers Can Create Invoices (grant Billing group)
+
+**Date:** 2026-05-29
+**Status:** Approved — implementing directly (single security record; no separate plan)
+**Module:** `fusion_plating_invoicing`
+
+## Goal
+
+Let the plating **Manager** role (and Quality Manager + Owner, who inherit it) create customer
+invoices from a confirmed Sale Order.
+
+## Background — why managers can't invoice today (verified 2026-05-29)
+
+- Creating an `account.move` of a customer type requires one of Odoo's accounting groups
+  (minimum: **Billing** = `account.group_account_invoice`).
+- **No plating role grants any Odoo accounting group.** A repo-wide grep for
+  `account.group_account*` in `fusion_plating*/security/` returns nothing.
+- `group_fp_manager` implies only the legacy plating-internal `group_fp_accounting`
+  (`fusion_plating_invoicing/security/fp_invoicing_security.xml:18-20`), which itself chains
+  to the deprecated `group_fusion_plating_supervisor` — **not** to any Odoo accounting group.
+  So it grants no `account.move` rights.
+- Result: when a Manager opens a confirmed SO and clicks **Create Invoice**, Odoo's
+  `_create_invoices()` tries to create an `account.move` and the Manager hits an `AccessError`
+  for lacking Billing.
+- Separately, `fusion_plating_jobs/models/account_move.py::_fp_validate_customer_invoice`
+  blocks off-SO customer-invoice creation for **all** users (parent-number audit trail). This
+  is a *workflow* gate, not a permission gate — it is **not** the manager blocker and stays
+  unchanged.
+
+## Decision
+
+Grant `account.group_account_invoice` (**Billing**) to `group_fp_manager` via `implied_ids`.
+
+- **Cascade:** Quality Manager → implies Manager, Owner → implies Quality Manager, so QM and
+  Owner inherit Billing automatically. Shop Manager, Sales Manager, Technician, Operator, and
+  below are **unaffected**.
+- **Level — Billing only:** create/edit/post customer invoices + credit notes. Explicitly
+  **not** Accountant (`account.group_account_user`): no vendor bills, manual journal entries,
+  bank reconciliation, accounting reports, or period close.
+- **Path unchanged:** managers invoice **from the SO** (`Create Invoice` action), which the
+  `_fp_validate_customer_invoice` workflow gate already permits via `fp_from_so_invoice`.
+  Standalone off-SO invoices remain blocked for everyone.
+
+## Implementation
+
+Extend the existing additive `implied_ids` write on `group_fp_manager` in
+`fusion_plating_invoicing/security/fp_invoicing_security.xml`:
+
+```xml
+<record id="fusion_plating.group_fp_manager" model="res.groups">
+    <field name="implied_ids" eval="[(4, ref('fusion_plating_invoicing.group_fp_accounting')),
+                                      (4, ref('account.group_account_invoice'))]"/>
+</record>
+```
+
+`(4, id)` (Command.link) is additive + idempotent across install/`-u`. `fusion_plating_invoicing`
+already depends transitively on `account` (it overrides `account.move`), so `ref('account.…')`
+resolves. Bump the module `version`.
+
+## Testing
+
+`TransactionCase` in `fusion_plating_invoicing/tests/`: create a user holding **only**
+`group_fp_manager`, assert `user.has_group('account.group_account_invoice')` is `True` (proves
+the implication landed). Then a live entech check: a Manager creates an invoice from a
+confirmed SO without an AccessError.
+
+## Out of scope
+
+- Relaxing the SO-origin workflow gate (intentional; preserves the parent-number audit trail).
+- Accountant-level access (vendor bills, journals, reconciliation, reports).
+- Granting invoicing to Shop Manager / Sales Manager / below.
diff --git a/fusion_plating/fusion_plating_invoicing/__manifest__.py b/fusion_plating/fusion_plating_invoicing/__manifest__.py
index 16bf70aa..01b3d662 100644
--- a/fusion_plating/fusion_plating_invoicing/__manifest__.py
+++ b/fusion_plating/fusion_plating_invoicing/__manifest__.py
@@ -5,7 +5,7 @@
 
 {
     'name': 'Fusion Plating — Invoicing',
-    'version': '19.0.3.7.0',
+    'version': '19.0.3.8.0',
     'category': 'Manufacturing/Plating',
     'summary': 'Invoice strategy engine with deposit, progress billing, net terms, COD/prepay, and account holds.',
     'description': """
diff --git a/fusion_plating/fusion_plating_invoicing/security/fp_invoicing_security.xml b/fusion_plating/fusion_plating_invoicing/security/fp_invoicing_security.xml
index 06b0669d..73cd595f 100644
--- a/fusion_plating/fusion_plating_invoicing/security/fp_invoicing_security.xml
+++ b/fusion_plating/fusion_plating_invoicing/security/fp_invoicing_security.xml
@@ -14,9 +14,15 @@
         <field name="user_ids" eval="[(4, ref('base.user_root')), (4, ref('base.user_admin'))]"/>
     </record>
 
-    <!-- Backward-compat: new Manager role implies old Accounting group. -->
+    <!-- Backward-compat: new Manager role implies old Accounting group.
+         2026-05-29: Manager (+ QM + Owner via implication) also gets Odoo's
+         Billing group so they can create customer invoices from a Sale
+         Order. Billing only — not Accountant. The SO-origin workflow gate
+         in fusion_plating_jobs is unchanged (off-SO invoices still blocked).
+         Spec: docs/superpowers/specs/2026-05-29-manager-invoice-permission-design.md -->
     <record id="fusion_plating.group_fp_manager" model="res.groups">
-        <field name="implied_ids" eval="[(4, ref('fusion_plating_invoicing.group_fp_accounting'))]"/>
+        <field name="implied_ids" eval="[(4, ref('fusion_plating_invoicing.group_fp_accounting')),
+                                         (4, ref('account.group_account_invoice'))]"/>
     </record>
 
 </odoo>
diff --git a/fusion_plating/fusion_plating_invoicing/tests/__init__.py b/fusion_plating/fusion_plating_invoicing/tests/__init__.py
new file mode 100644
index 00000000..e738dbb1
--- /dev/null
+++ b/fusion_plating/fusion_plating_invoicing/tests/__init__.py
@@ -0,0 +1,2 @@
+# -*- coding: utf-8 -*-
+from . import test_manager_invoice_permission
diff --git a/fusion_plating/fusion_plating_invoicing/tests/test_manager_invoice_permission.py b/fusion_plating/fusion_plating_invoicing/tests/test_manager_invoice_permission.py
new file mode 100644
index 00000000..1e756e63
--- /dev/null
+++ b/fusion_plating/fusion_plating_invoicing/tests/test_manager_invoice_permission.py
@@ -0,0 +1,36 @@
+# -*- coding: utf-8 -*-
+# Copyright 2026 Nexa Systems Inc.
+# License OPL-1 (Odoo Proprietary License v1.0)
+"""Manager (+ QM + Owner) imply Odoo Billing so they can invoice.
+
+Spec: docs/superpowers/specs/2026-05-29-manager-invoice-permission-design.md
+"""
+from odoo.tests.common import TransactionCase, tagged
+
+
+@tagged('post_install', '-at_install', 'fp_invoice_perm')
+class TestManagerInvoicePermission(TransactionCase):
+
+    def _user_with(self, group_xmlid):
+        return self.env['res.users'].create({
+            'name': 'PermUser',
+            'login': 'perm_%s' % group_xmlid.split('.')[-1],
+            'group_ids': [(6, 0, [self.env.ref(group_xmlid).id])],
+        })
+
+    def test_manager_has_billing_group(self):
+        manager = self._user_with('fusion_plating.group_fp_manager')
+        self.assertTrue(
+            manager.has_group('account.group_account_invoice'),
+            "Manager should imply Odoo Billing (account.group_account_invoice)",
+        )
+
+    def test_owner_inherits_billing(self):
+        owner = self._user_with('fusion_plating.group_fp_owner')
+        self.assertTrue(owner.has_group('account.group_account_invoice'))
+
+    def test_shop_manager_does_not_get_billing(self):
+        # Shop Manager is BELOW Manager — must NOT inherit Billing
+        # ("managers and ABOVE" scope).
+        shop = self._user_with('fusion_plating.group_fp_shop_manager_v2')
+        self.assertFalse(shop.has_group('account.group_account_invoice'))