Commercial fields are fields that are managed by the commercial entity to which a partner belongs. For example “vat” field is set in the parent company object and its value is transferred to all childs` contacts.
In case if you need to add a new field with the same functionality, then you would need to add the field in the res.partner model and to override the method _commercial_fields.
For example, let`s add the “credit_limit” field as a commercial field:
class ResPartner(models.Model): _inherit = "res.partner" credit_limit = fields.Float(string='Credit Limit') @api.model def _commercial_fields(self): return super(ResPartner, self)._commercial_fields() + ['credit_limit']