diff --git a/models/res_partner_contract.py b/models/res_partner_contract.py
index cc83d34..144d39a 100644
--- a/models/res_partner_contract.py
+++ b/models/res_partner_contract.py
@@ -4,10 +4,10 @@ from odoo import _, api, fields, models
 from odoo.tools.misc import DEFAULT_SERVER_DATE_FORMAT, DEFAULT_SERVER_DATETIME_FORMAT
 
 from ..utils import MODULE_NAME
-from ..utils.misc import Extension
+from ..utils.misc import Extension, IDocument
 
 
-class PartnerContract(models.Model, Extension):
+class PartnerContract(models.Model, IDocument, Extension):
     _name = "res.partner.contract"
     _description = "Contract"
     _inherit = ["mail.thread", "mail.activity.mixin", "mail.followers"]
diff --git a/models/res_partner_contract_annex.py b/models/res_partner_contract_annex.py
index 927e71b..a751955 100644
--- a/models/res_partner_contract_annex.py
+++ b/models/res_partner_contract_annex.py
@@ -3,10 +3,10 @@ import math
 from odoo import _, api, fields, models
 
 from ..utils import MODULE_NAME
-from ..utils.misc import Extension
+from ..utils.misc import Extension, IDocument
 
 
-class ContractOrderAnnex(models.Model, Extension):
+class ContractOrderAnnex(models.Model, IDocument, Extension):
     _name = "res.partner.contract.annex"
     _description = "Contract Annex"
 
diff --git a/utils/misc.py b/utils/misc.py
index 6df9bd5..d9c3c74 100644
--- a/utils/misc.py
+++ b/utils/misc.py
@@ -1,8 +1,20 @@
+import inspect
 import datetime as dt
 
+from odoo import fields
 from odoo.tools.misc import DEFAULT_SERVER_DATE_FORMAT, DEFAULT_SERVER_DATETIME_FORMAT
 
 
+class IDocument(object):
+    """Class must be used as an interface for create new document based model"""
+
+    def get_name_by_document_template(self, document_template_id: fields.Many2one):
+        raise NotImplementedError('Method {} is not implemented'.format(inspect.currentframe().f_code.co_name))
+
+    def get_filename_by_document_template(self, document_template_id: fields.Many2one):
+        raise NotImplementedError('Method {} is not implemented'.format(inspect.currentframe().f_code.co_name))
+
+
 class Extension(object):
 
     def parse_odoo_date(self, date: str):