diff --git a/fusion_centralize_billing/models/usage.py b/fusion_centralize_billing/models/usage.py
index f8e12658..63dde5eb 100644
--- a/fusion_centralize_billing/models/usage.py
+++ b/fusion_centralize_billing/models/usage.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # Copyright 2026 Nexa Systems Inc.
 # License OPL-1
-from odoo import fields, models
+from odoo import api, fields, models
 
 
 class FusionBillingUsage(models.Model):
@@ -37,3 +37,24 @@ class FusionBillingUsage(models.Model):
     _idempotency_uniq = models.Constraint(
         "unique(idempotency_key)", "Usage idempotency key must be unique.",
     )
+
+    @api.model
+    def _record_usage(self, subscription, metric_code, quantity, period_start, period_end, idem=None):
+        """Upsert one aggregated usage row. Same idempotency key updates in place (no double-count)."""
+        metric = self.env['fusion.billing.metric'].search([('code', '=', metric_code)], limit=1)
+        if not metric:
+            raise ValueError("Unknown metric code: %s" % metric_code)
+        vals = {
+            'subscription_id': subscription.id,
+            'metric_id': metric.id,
+            'period_start': period_start,
+            'period_end': period_end,
+            'quantity': quantity,
+            'idempotency_key': idem,
+        }
+        if idem:
+            existing = self.search([('idempotency_key', '=', idem)], limit=1)
+            if existing:
+                existing.write({'quantity': quantity})
+                return existing
+        return self.create(vals)
diff --git a/fusion_centralize_billing/tests/__init__.py b/fusion_centralize_billing/tests/__init__.py
index 23d9aa9c..07117e0d 100644
--- a/fusion_centralize_billing/tests/__init__.py
+++ b/fusion_centralize_billing/tests/__init__.py
@@ -1,2 +1,3 @@
 from . import test_identity
 from . import test_charge
+from . import test_usage
diff --git a/fusion_centralize_billing/tests/test_usage.py b/fusion_centralize_billing/tests/test_usage.py
new file mode 100644
index 00000000..10475bba
--- /dev/null
+++ b/fusion_centralize_billing/tests/test_usage.py
@@ -0,0 +1,33 @@
+# -*- coding: utf-8 -*-
+from odoo.tests.common import TransactionCase, tagged
+
+
+@tagged('post_install', '-at_install')
+class TestUsageIngestion(TransactionCase):
+
+    def setUp(self):
+        super().setUp()
+        self.metric = self.env['fusion.billing.metric'].sudo().create(
+            {'name': 'CPU seconds', 'code': 'cpu_seconds', 'aggregation': 'sum'})
+        self.plan = self.env['sale.subscription.plan'].sudo().create(
+            {'name': 'Monthly', 'billing_period_value': 1, 'billing_period_unit': 'month'})
+        self.partner = self.env['res.partner'].sudo().create({'name': 'Acme'})
+        self.sub = self.env['sale.order'].sudo().create({
+            'partner_id': self.partner.id, 'is_subscription': True, 'plan_id': self.plan.id,
+        })
+        self.Usage = self.env['fusion.billing.usage'].sudo()
+
+    def test_record_usage_creates_row(self):
+        u = self.Usage._record_usage(
+            self.sub, 'cpu_seconds', 120.0,
+            '2026-05-01 00:00:00', '2026-06-01 00:00:00', idem='nexacloud:cpu:sub1:2026-05-01')
+        self.assertEqual(u.quantity, 120.0)
+        self.assertEqual(u.metric_id, self.metric)
+
+    def test_idempotent_key_updates_not_duplicates(self):
+        k = 'nexacloud:cpu:sub1:2026-05-01'
+        self.Usage._record_usage(self.sub, 'cpu_seconds', 100.0, '2026-05-01', '2026-06-01', idem=k)
+        self.Usage._record_usage(self.sub, 'cpu_seconds', 175.0, '2026-05-01', '2026-06-01', idem=k)
+        rows = self.Usage.search([('idempotency_key', '=', k)])
+        self.assertEqual(len(rows), 1)        # no duplicate
+        self.assertEqual(rows.quantity, 175.0)  # last value wins for the same key