diff --git a/docsource/development.rst b/docsource/development.rst
index 16972978d40a..62f9e6dcba53 100644
--- a/docsource/development.rst
+++ b/docsource/development.rst
@@ -60,6 +60,7 @@ Learn from typical Use cases
    use_cases/xml_id_renaming
    use_cases/module_renaming
    use_cases/noupdate_xml_entry_changed
+   use_cases/format_value_changing
    use_cases/value_mapping
    use_cases/sql_constraint_deleted
 
diff --git a/docsource/use_cases/format_value_changing.rst b/docsource/use_cases/format_value_changing.rst
new file mode 100644
index 000000000000..b4c18d56f896
--- /dev/null
+++ b/docsource/use_cases/format_value_changing.rst
@@ -0,0 +1,133 @@
+Format Value Changing
++++++++++++++++++++++
+
+Example
+-------
+
+From version 14.0 to version 15.0, the field ``description`` of the model ``hr.job``
+is changed his type from ``fields.Text`` to ``fields.Html``.
+
+Source Code Differences
+-----------------------
+
+Version 14.0
+""""""""""""
+
+.. code-block:: python
+
+    class HrJob(models.Model):
+        _name = "hr.job"
+
+        description = fields.Text(string='Job Description')
+
+See `Full v14 Code Source <https://github.com/odoo/odoo/blob/f71626fa6ba413625d7242f5e13d05b8b95be48c/addons/hr/models/hr_job.py#L23>`_.
+
+
+Version 15.0
+""""""""""""
+
+.. code-block:: python
+
+    class HrJob(models.Model):
+        _name = "hr.job"
+
+        description = fields.Html(string='Job Description')
+
+
+See `Full v15 Code Source <https://github.com/odoo/odoo/blob/ca7400f22258706f3d989c2008062648050b5b50/addons/hr/models/hr_job.py#L26>`_.
+
+
+Analysis
+--------
+
+.. code-block:: text
+
+    ...
+    ---Fields in module 'hr'---
+    ...
+    hr           / hr.job                   / description (text)            : type is now 'html' ('text')
+
+
+See `Full V15 Analysis File <https://github.com/OCA/OpenUpgrade/blob/15.0/openupgrade_scripts/scripts/hr/15.0.1.1/upgrade_analysis.txt>`_.
+
+Result without migration script / Expected Result
+-------------------------------------------------
+
+V14 table ``hr_job``
+""""""""""""""""""""
+
+.. csv-table::
+   :header: "id", "name", "description"
+
+   "50", "OpenUpgrade Expert", "the candidate must have read the documentation at this url :\n\nhttps://oca.github.io/OpenUpgrade"
+
+
+V15 table ``hr_job`` (Without openupgrade)
+""""""""""""""""""""""""""""""""""""""""""
+
+.. csv-table::
+   :header: "id", "name", "description"
+
+   "50", "OpenUpgrade Expert", "<p>the candidate must have read the documentation at this url : </p><p><a href="https://oca.github.io/OpenUpgrade/" target="_blank" rel="noreferrer noopener">https://oca.github.io/OpenUpgrade/</a></p>"
+
+**Problem**:
+
+The data has not been converted in HTML.
+
+V15 table ``hr_job`` (With openupgrade)
+"""""""""""""""""""""""""""""""""""""""
+
+.. csv-table::
+   :header: "id", "name", "description"
+
+   "50", "OpenUpgrade Expert", "<p>the candidate must have read the documentation at this url : </p><p><a href="https://oca.github.io/OpenUpgrade/" target="_blank" rel="noreferrer noopener">https://oca.github.io/OpenUpgrade/</a></p>"
+
+Contribution to OpenUpgrade
+---------------------------
+
+Update ``upgrade_analysis_work.txt`` file
+"""""""""""""""""""""""""""""""""""""""""
+
+Add a comment after the line:
+
+.. code-block:: text
+
+    hr      / hr.job        / description (text)        : type is now 'html' ('text')
+    # DONE pre-migration: convert to html
+
+
+See `Full v15 Work Analysis File <https://github.com/OCA/OpenUpgrade/blob/15.0/openupgrade_scripts/scripts/hr/15.0.1.1/upgrade_analysis_work.txt>`_.
+
+Write migration Script
+""""""""""""""""""""""
+
+in the ``pre-migration.py`` script add:
+
+.. code-block:: python
+
+    from openupgradelib import openupgrade
+
+
+    @openupgrade.migrate()
+    def migrate(env, version):
+        openupgrade.convert_field_to_html(env.cr, "hr_job", "description", "description")
+
+See `Full V15 pre migration Script <https://github.com/OCA/OpenUpgrade/blob/15.0/openupgrade_scripts/scripts/hr/15.0.1.1/pre-migration.py>`_.
+
+
+Notes
+-----
+
+there are several other functions that handle field type changes:
+
+* **convert_field_to_html** : to transform a ``field.Date()`` into a ``field.Datetime()``,
+  with correct timezone management.
+  (otherwise, all datetimes will have a number of offset hours,
+  corresponding to the difference between the administrator's timezone and greenwitch's timezone
+  at the time of migration)
+
+**float_to_integer** : to transform a ``field.Float()`` into a ``field.Integer()``,
+  truncating the decimal value.
+  (If not done, the value will be rounded by odoo ORM)
+
+**m2o_to_x2m** : to transform a ``field.Many2one()`` into a ``field.Many2many()`` or ``field.One2many()``.