Add completion rule to complete from SO payment ref

account_move_so_import/data/completion_rule_data.xml

@@ -7,4 +7,10 @@
         <field name="function_to_call">get_from_name_and_so</field>
     </record>
 
+    <record id="bank_statement_completion_rule_2" model="account.move.completion.rule">
+        <field name="name">Match from line name (based on SO payment reference)</field>
+        <field name="sequence">55</field>
+        <field name="function_to_call">get_from_name_and_so_payment_ref</field>
+    </record>
+
 </odoo>

account_move_so_import/models/account_move.py

@@ -11,7 +11,13 @@ class AccountMoveCompletionRule(models.Model):
     _inherit = "account.move.completion.rule"
 
     function_to_call = fields.Selection(
-        selection_add=[("get_from_name_and_so", "From line name (based on SO number)")]
+        selection_add=[
+            ("get_from_name_and_so", "From line name (based on SO number)"),
+            (
+                "get_from_name_and_so_payment_ref",
+                "From line name (based on SO payment ref)",
+            ),
+        ]
     )
 
     # Should be private but data are initialized with no update XML
@@ -47,3 +53,32 @@ class AccountMoveCompletionRule(models.Model):
         if len(orders) == 1:
             res["partner_id"] = orders[0].partner_id.id
         return res
+
+    # Should be private but data are initialized with no update XML
+    def get_from_name_and_so_payment_ref(self, line):
+        """
+        :param int/long st_line: read of the concerned
+        account.bank.statement.line
+
+        :return:
+            A dict of value that can be passed directly to the write method of
+            the statement line or {}
+           {'partner_id': value,
+            'account_id': value,
+
+            ...}
+        """
+        res = {}
+        so_obj = self.env["sale.order"]
+        orders = so_obj.search([("reference", "=", line.name)])
+        if len(orders) > 1:
+            raise ErrorTooManyPartner(
+                _(
+                    'Line named "%s"  was matched by more '
+                    "than one partner while looking on SO by ref."
+                )
+                % line.name
+            )
+        if len(orders) == 1:
+            res["partner_id"] = orders[0].partner_id.id
+        return res

account_move_so_import/tests/test_completion_so.py

@@ -16,6 +16,7 @@ class TestCompliteSO(SavepointCase):
             {
                 "name": "Test order",
                 "partner_id": cls.partner.id,
+                "reference": "test payment ref",
                 "order_line": [
                     (
                         0,
@@ -48,6 +49,9 @@ class TestCompliteSO(SavepointCase):
         rule_ids += cls.env.ref(
             "account_move_so_import." "bank_statement_completion_rule_1"
         )
+        rule_ids += cls.env.ref(
+            "account_move_so_import." "bank_statement_completion_rule_2"
+        )
         # create journal with profile
         cls.journal = cls.env["account.journal"].create(
             {
@@ -81,9 +85,9 @@ class TestCompliteSO(SavepointCase):
             ],
             limit=1,
         )
+        cls.order.action_confirm()
 
-    def test_completion_so(self):
-        self.order.action_confirm()
+    def test_completion_so_name(self):
         self.env["account.move.line"].create(
             [
                 {
@@ -109,3 +113,30 @@ class TestCompliteSO(SavepointCase):
             payable_aml.partner_id,
             self.partner,
         )
+
+    def test_completion_so_payment_ref(self):
+        self.env["account.move.line"].create(
+            [
+                {
+                    "name": self.order.reference,
+                    "account_id": self.account_payable.id,
+                    "move_id": self.move.id,
+                    "credit": 1,
+                },
+                {
+                    "name": "counter part",
+                    "account_id": self.account_bank.id,
+                    "move_id": self.move.id,
+                    "debit": 1,
+                },
+            ]
+        )
+        payable_aml = self.move.line_ids.filtered(
+            lambda line: line.account_id == self.account_payable
+        )
+        self.assertFalse(self.move.partner_id)
+        self.move.button_auto_completion()
+        self.assertEqual(
+            payable_aml.partner_id,
+            self.partner,
+        )