diff --git a/account_invoice_same_accounting_date/models/account_move.py b/account_invoice_same_accounting_date/models/account_move.py
index 786778705..17743e846 100644
--- a/account_invoice_same_accounting_date/models/account_move.py
+++ b/account_invoice_same_accounting_date/models/account_move.py
@@ -2,13 +2,27 @@
 # Eric Antones <eantones@nuobit.com>
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl)
 
-
-from odoo import api, models
+from odoo import models
 
 
 class AccountMove(models.Model):
     _inherit = "account.move"
 
-    @api.onchange("invoice_date")
-    def _onchange_invoice_date_accounting(self):
-        self.date = self.invoice_date
+    def _get_accounting_date(self, invoice_date, has_tax):
+        # For purchase documents, we want the same behavior as sale documents
+        # in super: apply the tax lock date check and return invoice_date
+        # (instead of max(invoice_date, today) which is the purchase default).
+        # The simpler approach would be to duplicate the tax lock date check
+        # from super, but we prefer not to duplicate code. Instead, we
+        # temporarily flag the context so is_sale_document() returns True
+        # during this specific super call, making it take the sale branch
+        # which does exactly what we need. The flag is scoped to this call
+        # only and does not affect any other use of is_sale_document().
+        if self.is_purchase_document(include_receipts=True) and invoice_date:
+            self = self.with_context(_force_invoice_accounting_date=True)
+        return super(AccountMove, self)._get_accounting_date(invoice_date, has_tax)
+
+    def is_sale_document(self, include_receipts=False):
+        if self._context.get("_force_invoice_accounting_date"):
+            return True
+        return super().is_sale_document(include_receipts=include_receipts)
diff --git a/account_invoice_same_accounting_date_prorate/models/account_move.py b/account_invoice_same_accounting_date_prorate/models/account_move.py
index 59b80a6e6..3a6497ef5 100644
--- a/account_invoice_same_accounting_date_prorate/models/account_move.py
+++ b/account_invoice_same_accounting_date_prorate/models/account_move.py
@@ -2,16 +2,16 @@
 # Eric Antones <eantones@nuobit.com>
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl)
 
-
 from odoo import api, models
 
 
 class AccountMove(models.Model):
     _inherit = "account.move"
 
-    @api.onchange("invoice_date")
-    def _onchange_invoice_date_accounting(self):
-        super()._onchange_invoice_date_accounting()
-        self._recompute_dynamic_lines(
-            recompute_all_taxes=True, recompute_tax_base_amount=True
-        )
+    @api.onchange("invoice_date", "highest_name", "company_id")
+    def _onchange_invoice_date(self):
+        super()._onchange_invoice_date()
+        if self.line_ids.tax_ids.filtered("prorate"):
+            self._recompute_dynamic_lines(
+                recompute_all_taxes=True, recompute_tax_base_amount=True
+            )