diff --git a/python_ifirma/core.py b/python_ifirma/core.py
index 086213e..223a87e 100644
--- a/python_ifirma/core.py
+++ b/python_ifirma/core.py
@@ -160,12 +160,31 @@ class iFirmaAPI():
 
     def generate_invoice(self, invoice):
         url = "https://www.ifirma.pl/iapi/fakturakraj.json"
-        return self.__create_invoice_and_return_id(invoice, url)
+        invoice_id = self.__create_invoice_and_return_id(invoice, url)
+        if invoice_id:
+            invoice_number = self.__get_invoice_number(invoice_id)
+            return invoice_id, invoice_number
+        return None, None
 
     def get_invoice_pdf(self, invoice_id):
         url = "https://www.ifirma.pl/iapi/fakturakraj/{}.pdf".format(invoice_id)
         return self.__download_pdf(url)
 
+    def __get_invoice_number(self, invoice_id):
+        url = "https://www.ifirma.pl/iapi/fakturakraj/{}.json".format(invoice_id)
+        request_hash_text = "{}{}{}".format(
+            url,
+            self.__username,
+            self.__invoice_key_name,
+        )
+        headers = {
+            "Accept": "application/json",
+            "Content-type": "application/json; charset=UTF-8",
+            "Authentication": self.__create_authentication_header_value(request_hash_text)
+        }
+        resp = requests.get(url, headers=headers)
+        return json.loads(resp.content.decode('utf-8'))["response"]["PelnyNumer"]
+
     def __download_pdf(self, url):
         request_hash_text = "{}{}{}".format(
             url,
diff --git a/python_ifirma/tests.py b/python_ifirma/tests.py
index b768266..246b9a3 100644
--- a/python_ifirma/tests.py
+++ b/python_ifirma/tests.py
@@ -117,6 +117,8 @@ class TestCreateInvoice(TestCase):
 
     def test_download_invoice(self):
         invoice = NewInvoiceParams(self.client, [self.position])
-        invoice_id = self.ifirma_client.generate_invoice(invoice)
+        invoice_id, invoice_number = self.ifirma_client.generate_invoice(invoice)
 
+        self.assertIsNotNone(invoice_id)
+        self.assertIsNotNone(invoice_number)
         self.assertIsNotNone(self.ifirma_client.get_invoice_pdf(invoice_id))
\ No newline at end of file
diff --git a/readme.md b/readme.md
index 4f4727c..fa84ec4 100644
--- a/readme.md
+++ b/readme.md
@@ -55,16 +55,16 @@ client = Client(
 position = Position(
     VAT.VAT_23,  # VAT rate 
     1,  # Quantity
-    1000,  # Unit price
+    1000.00,  # Unit total price
     "nazwa",  # Position name
     "szt"  # Position unit
 )
 ```
 
-#####3. Create invoice in iFirma service and get it's id
+#####3. Create invoice in iFirma service and get it's id and number
 ```python
 invoice = NewInvoiceParams(client, [position])
-invoice_id = ifirma_client.generate_invoice(invoice)
+invoice_id, invoice_number = ifirma_client.generate_invoice(invoice)
 ```
 
 #####4. Download invoice PDF
diff --git a/setup.py b/setup.py
index 5651a90..2eaee35 100644
--- a/setup.py
+++ b/setup.py
@@ -2,7 +2,7 @@ from setuptools import setup, find_packages
 
 setup(
     name="python-ifirma",
-    version="0.0.3",
+    version="0.0.5",
     packages=find_packages(),
     install_requires=[
         'requests',