diff --git a/base_jsonify/models/models.py b/base_jsonify/models/models.py
index eb30002db..f75d8f21b 100644
--- a/base_jsonify/models/models.py
+++ b/base_jsonify/models/models.py
@@ -1,6 +1,8 @@
-# © 2017 Akretion (http://www.akretion.com)
+# Copyright 2017 Akretion (http://www.akretion.com)
 # Sébastien BEAU <sebastien.beau@akretion.com>
 # Raphaël Reverdy <raphael.reverdy@akretion.com>
+# Copyright 2020 Camptocamp SA (http://www.camptocamp.com)
+# Simone Orsi <simahawk@gmail.com>
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
 
 from odoo import api, fields, models
@@ -33,6 +35,8 @@ class Base(models.AbstractModel):
                 'number',
                 'create_date',
                 ('partner_id', ['id', 'display_name', 'ref'])
+                ('shipping_id', callable)
+                ('delivery_id', "record_method")
                 ('line_id', ['id', ('product_id', ['name']), 'price_unit'])
             ]
 
@@ -64,6 +68,7 @@ class Base(models.AbstractModel):
     def _jsonify_value(self, field_name):
         field_type = self._fields[field_name].type
         value = self[field_name]
+        # TODO: we should get default by field (eg: char field -> "")
         if value is False and field_type != "boolean":
             value = None
         elif field_type == "date":
@@ -79,15 +84,26 @@ class Base(models.AbstractModel):
         return value
 
     def _jsonify_value_subparser(self, field_name, subparser):
-        field_type = self._fields[field_name].type
-        if field_type in ("one2many", "many2many"):
-            value = self[field_name].jsonify(subparser)
-        elif field_type in ("many2one", "reference"):
-            if self[field_name]:
-                value = self[field_name].jsonify(subparser)[0]
+        value = None
+        if callable(subparser):
+            # a simple function
+            value = subparser(self, field_name)
+        elif isinstance(subparser, str):
+            # a method on the record itself
+            method = getattr(self, subparser, None)
+            if method:
+                value = method(field_name)
             else:
-                # TODO: we should get this by field (eg: char field -> "")
-                value = None
+                self._jsonify_bad_parser_error(field_name)
         else:
-            raise UserError(_("Wrong parser configuration"))
+            field = self._fields[field_name]
+            if not (field.relational or field.type == "reference"):
+                self._jsonify_bad_parser_error(field_name)
+            rec_value = self[field_name]
+            value = rec_value.jsonify(subparser) if rec_value else []
+            if field.type in ("many2one", "reference"):
+                value = value[0] if value else None
         return value
+
+    def _jsonify_bad_parser_error(self, field_name):
+        raise UserError(_("Wrong parser configuration for field: `%s`") % field_name)
diff --git a/base_jsonify/readme/DESCRIPTION.rst b/base_jsonify/readme/DESCRIPTION.rst
index 115e75c0d..93012ac1c 100644
--- a/base_jsonify/readme/DESCRIPTION.rst
+++ b/base_jsonify/readme/DESCRIPTION.rst
@@ -39,5 +39,15 @@ can define your mapping as follow into the parser definition:
         ('line_id:lines', ['id', ('product_id', ['name']), 'price_unit'])
     ]
 
+If you need to parse the value of a field in a custom way,
+you can pass a callable or the name of a method on the model:
+
+.. code-block:: python
+
+    parser = [
+        ('name', "jsonify_name")  # method name
+        ('number', lambda rec, field_name: rec[field_name] * 2))  # callable
+    ]
+
 Also the module provide a method "get_json_parser" on the ir.exports object
 that generate a parser from an ir.exports configuration.
diff --git a/base_jsonify/tests/test_get_parser.py b/base_jsonify/tests/test_get_parser.py
index 9c9b79a32..9e616025d 100644
--- a/base_jsonify/tests/test_get_parser.py
+++ b/base_jsonify/tests/test_get_parser.py
@@ -5,6 +5,10 @@ from odoo import fields
 from odoo.tests.common import TransactionCase
 
 
+def jsonify_custom(self, field_name):
+    return "yeah!"
+
+
 class TestParser(TransactionCase):
     def test_getting_parser(self):
         expected_parser = [
@@ -114,10 +118,6 @@ class TestParser(TransactionCase):
 
         self.assertDictEqual(json_partner[0], expected_json)
 
-        json_partner = partner.jsonify(parser)
-
-        self.assertDictEqual(json_partner[0], expected_json)
-
         # Check that only boolean fields have boolean values into json
         # By default if a field is not set into Odoo, the value is always False
         # This value is not the expected one into the json
@@ -127,3 +127,38 @@ class TestParser(TransactionCase):
         expected_json["lang"] = None
         expected_json["children"] = []
         self.assertDictEqual(json_partner[0], expected_json)
+
+    def test_json_export_callable_parser(self):
+        # Enforces TZ to validate the serialization result of a Datetime
+        partner = self.env["res.partner"].create(
+            {
+                "name": "Akretion",
+                "country_id": self.env.ref("base.fr").id,
+                "lang": "en_US",  # default
+                "category_id": [(0, 0, {"name": "Inovator"})],
+                "child_ids": [
+                    (
+                        0,
+                        0,
+                        {
+                            "name": "Sebatien Beau",
+                            "country_id": self.env.ref("base.fr").id,
+                        },
+                    )
+                ],
+                "date": fields.Date.from_string("2019-10-31"),
+            }
+        )
+        partner.__class__.jsonify_custom = jsonify_custom
+        parser = [
+            # callable subparser
+            ("name", lambda rec, fname: rec[fname] + " rocks!"),
+            ("name:custom", "jsonify_custom"),
+        ]
+        expected_json = {
+            "name": "Akretion rocks!",
+            "custom": "yeah!",
+        }
+        json_partner = partner.jsonify(parser)
+        self.assertDictEqual(json_partner[0], expected_json)
+        del partner.__class__.jsonify_custom