diff --git a/eopayment/sips2.py b/eopayment/sips2.py
index ee8b7d1..8e7291d 100644
--- a/eopayment/sips2.py
+++ b/eopayment/sips2.py
@@ -16,13 +16,11 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import datetime
-from decimal import Decimal
 from gettext import gettext as _
 import collections
 import hashlib
 import hmac
 import json
-import string
 import uuid
 import warnings
 
@@ -196,11 +194,13 @@ class Payment(PaymentCommon):
 
     def request(self, amount, name=None, first_name=None, last_name=None,
                 address=None, email=None, phone=None, orderid=None,
-                info1=None, info2=None, info3=None, next_url=None, **kwargs):
+                info1=None, info2=None, info3=None, next_url=None, transaction_id=None, **kwargs):
         data = self.get_data()
-        transaction_id = self.transaction_id(10, string.digits, 'sips2', data['merchantId'])
-        data['transactionReference'] = force_text(transaction_id)
-        data['orderId'] = orderid or force_text(uuid.uuid4()).replace('-', '')
+        # documentation:
+        # https://documentation.sips.worldline.com/fr/WLSIPS.801-MG-Presentation-generale-de-la-migration-vers-Sips-2.0.html#ariaid-title20
+        transactionReference = transaction_id or uuid.uuid4().hex
+        data['transactionReference'] = transactionReference
+        data['orderId'] = orderid or transactionReference
         if info1:
             data['statementReference'] = force_text(info1)
         else:
@@ -238,7 +238,7 @@ class Payment(PaymentCommon):
                 },
             ])
         self.logger.debug('emitting request %r', data)
-        return transaction_id, FORM, form
+        return transactionReference, FORM, form
 
     def decode_data(self, data):
         data = data.split('|')