diff --git a/l10n_es_edi_tbai_reagyp_recibidas/models/__init__.py b/l10n_es_edi_tbai_reagyp_recibidas/models/__init__.py
index e89b491..265dbff 100644
--- a/l10n_es_edi_tbai_reagyp_recibidas/models/__init__.py
+++ b/l10n_es_edi_tbai_reagyp_recibidas/models/__init__.py
@@ -1 +1,3 @@
 from . import account_move  # noqa: F401
+from . import res_company  # noqa: F401
+from . import l10n_es_edi_tbai_document  # noqa: F401
diff --git a/l10n_es_edi_tbai_reagyp_recibidas/models/l10n_es_edi_tbai_document.py b/l10n_es_edi_tbai_reagyp_recibidas/models/l10n_es_edi_tbai_document.py
new file mode 100644
index 0000000..9f06ffa
--- /dev/null
+++ b/l10n_es_edi_tbai_reagyp_recibidas/models/l10n_es_edi_tbai_document.py
@@ -0,0 +1,62 @@
+# Copyright 2026 - Today Criptomart
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+import re
+
+from odoo import models
+
+
+class L10nEsEdiTbaiDocument(models.Model):
+    _inherit = "l10n_es_edi_tbai.document"
+
+    def _get_sale_values(self, values):
+        """Override to ensure chain links only within the same invoice series."""
+        sale_values = super()._get_sale_values(values)
+
+        # Replace chain_prev_document with one from the same series
+        chain_prev_document = sale_values.get("chain_prev_document")
+        if chain_prev_document:
+            current_series = self._get_series_prefix(self.name)
+            prev_series = self._get_series_prefix(chain_prev_document.name)
+
+            # If series mismatch OR previous doc has no valid XML, find correct one
+            if (
+                current_series != prev_series
+                or not chain_prev_document.xml_attachment_id
+            ):
+                same_series_doc = self._get_last_chained_document_by_series(
+                    current_series
+                )
+                sale_values["chain_prev_document"] = same_series_doc
+
+        return sale_values
+
+    @staticmethod
+    def _get_series_prefix(doc_name):
+        """Extract series prefix from document name (e.g., 'INV/2026/' from 'INV/2026/01248')."""
+        if not doc_name:
+            return ""
+        # Everything before the first digit
+        match = re.search(r"\d+", doc_name)
+        if match:
+            return doc_name[: match.start()].rstrip("/")
+        return doc_name
+
+    def _get_last_chained_document_by_series(self, series_prefix):
+        """Find the last valid chained document matching a specific series prefix."""
+        domain = [
+            ("chain_index", "!=", 0),
+            ("company_id", "=", self.company_id.id),
+            ("is_cancel", "=", False),
+            ("state", "=", "accepted"),  # Must be accepted in chain
+        ]
+        docs = self.search(domain, order="chain_index desc")
+
+        # Return the first doc matching series that has valid XML
+        for doc in docs:
+            if (
+                self._get_series_prefix(doc.name) == series_prefix
+                and doc.xml_attachment_id
+            ):
+                return doc
+
+        return self.env["l10n_es_edi_tbai.document"]
diff --git a/l10n_es_edi_tbai_reagyp_recibidas/models/res_company.py b/l10n_es_edi_tbai_reagyp_recibidas/models/res_company.py
new file mode 100644
index 0000000..179e146
--- /dev/null
+++ b/l10n_es_edi_tbai_reagyp_recibidas/models/res_company.py
@@ -0,0 +1,22 @@
+# Copyright 2026 - Today Criptomart
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+from odoo import models
+
+
+class ResCompany(models.Model):
+    _inherit = "res.company"
+
+    def _get_l10n_es_tbai_last_chained_document(self):
+        """
+        Returns the last tbai document posted to this company's chain.
+        Each invoice series has its own independent chain in TicketBAI.
+        Filters out cancellation documents to skip cancelled invoices.
+        """
+        domain = [
+            ("chain_index", "!=", 0),
+            ("company_id", "=", self.id),
+            ("is_cancel", "=", False),
+        ]
+        return self.env["l10n_es_edi_tbai.document"].search(
+            domain, limit=1, order="chain_index desc"
+        )