diff --git a/README.md b/README.md
index adde998d7..cbfc21824 100644
--- a/README.md
+++ b/README.md
@@ -155,7 +155,7 @@ DNS name or IP address of the server hosting the elasticSearch database.
     SECRET_KEY_BASE
 
 Used by the authentication system to generate random tokens, eg. for resetting passwords.
-Used by Rails to generate the integrity of signed cookies.
+Used by Rails to verify the integrity of signed cookies.
 You can generate such a random key by running `rake secret`.
 
     STRIPE_API_KEY & STRIPE_PUBLISHABLE_KEY
@@ -174,8 +174,8 @@ So set this setting carefully before starting the application for the first time
 
     INVOICE_PREFIX
 
-When payments are done on the platform, an invoice will be generate as a PDF file.
-This value configure the prefix of the PDF file name.
+When payments are done on the platform, an invoice will be generated as a PDF file.
+The PDF file name will be of the form "(INVOICE_PREFIX) - (invoice ID) _ (invoice date) .pdf"
 
     FABLAB_WITHOUT_PLANS
 
@@ -203,7 +203,7 @@ Identifier of your Google Analytics account.
     DISQUS_SHORTNAME
 
 Unique identifier of your [Disqus](http://www.disqus.com) forum.
-Disquq forums are used to allow visitors to comment on projects.
+Disqus forums are used to allow visitors to comment on projects.
 See https://help.disqus.com/customer/portal/articles/466208-what-s-a-shortname- for more informations.
 
     TWITTER_NAME
@@ -213,6 +213,7 @@ Identifier of the Twitter account, for witch the last tweet will be displayed on
     TWITTER_CONSUMER_KEY, TWITTER_CONSUMER_SECRET, TWITTER_ACCESS_TOKEN & TWITTER_ACCESS_TOKEN_SECRET
 
 Keys and secrets to access the twitter API.
+Retrieve them from https://apps.twitter.com
 
     Settings related to i18n
 
@@ -443,7 +444,9 @@ If you are in a development environment, your can keep the default values, other
 #### Settings
     RAILS_LOCALE
 
-Be sure that `config/locales/rails.XX.yml` exists, where `XX` match your configured rails_locale. 
+Configure Ruby on Rails for l10n.
+
+Be sure that `config/locales/rails.XX.yml` exists, where `XX` match your configured RAILS_LOCALE. 
 You can find templates of these files at https://github.com/svenfuchs/rails-i18n/tree/rails-4-x/rails/locale.
 
 Be aware that **this file MUST contain the CURRENCY symbol used to generate invoices** (among other things). 
diff --git a/app/assets/templates/admin/invoices/index.html.erb b/app/assets/templates/admin/invoices/index.html.erb
index 4c96d3789..11d7b2ee3 100644
--- a/app/assets/templates/admin/invoices/index.html.erb
+++ b/app/assets/templates/admin/invoices/index.html.erb
@@ -154,11 +154,11 @@
 
               <tr class="invoice-vat invoice-editable vat-line italic" ng-click="openEditVAT()" ng-show="invoice.VAT.active">
                   <td>{{ 'including_VAT' | translate }} {{invoice.VAT.rate}} %</td>
-                  <td>{{30*invoice.VAT.rate/100 | currency}}</td>
+                  <td>{{30/(invoice.VAT.rate/100+1) | currency}}</td>
               </tr>
               <tr class="invoice-ht vat-line italic" ng-show="invoice.VAT.active">
                   <td translate>{{ 'including_total_excluding_taxes' }}</td>
-                  <td>{{30-(30*invoice.VAT.rate/100) | currency}}</td>
+                  <td>{{30-(30/(invoice.VAT.rate/100+1)) | currency}}</td>
               </tr>
               <tr class="invoice-payed vat-line bold" ng-show="invoice.VAT.active">
                   <td translate>{{ 'including_amount_payed_on_ordering' }}</td>
diff --git a/app/models/invoice.rb b/app/models/invoice.rb
index 0421c364d..787eec524 100644
--- a/app/models/invoice.rb
+++ b/app/models/invoice.rb
@@ -117,7 +117,7 @@ class Invoice < ActiveRecord::Base
     reference
   end
 
-  # only for debug
+  # for debug & used by rake task "fablab:regenerate_invoices"
   def regenerate_invoice_pdf
     pdf = ::PDF::Invoice.new(self).render
     File.binwrite(file, pdf)
diff --git a/app/pdfs/pdf/invoice.rb b/app/pdfs/pdf/invoice.rb
index 9651cca61..ce890dad0 100644
--- a/app/pdfs/pdf/invoice.rb
+++ b/app/pdfs/pdf/invoice.rb
@@ -138,7 +138,7 @@ module PDF
           data += [ [I18n.t('invoices.total_including_all_taxes'), number_to_currency(total)] ]
 
           vat_rate = Setting.find_by({name: 'invoice_VAT-rate'}).value.to_f
-          vat = total * vat_rate / 100
+          vat = total / (vat_rate / 100 + 1)
           data += [ [I18n.t('invoices.including_VAT_RATE', RATE: vat_rate), number_to_currency(vat)] ]
           data += [ [I18n.t('invoices.including_total_excluding_taxes'), number_to_currency(total-vat)] ]
           data += [ [I18n.t('invoices.including_amount_payed_on_ordering'), number_to_currency(total)] ]
diff --git a/lib/tasks/fablab.rake b/lib/tasks/fablab.rake
index 5ca3a43fa..32c3b4010 100644
--- a/lib/tasks/fablab.rake
+++ b/lib/tasks/fablab.rake
@@ -26,14 +26,7 @@ namespace :fablab do
     start_date = Time.new(year.to_i, month.to_i, 1)
     end_date = start_date.next_month
     puts "-> Start regenerate the invoices between #{I18n.l start_date, format: :long} in #{I18n.l end_date-1.minute, format: :long}"
-    index = '000'
     invoices = Invoice.only_invoice.where("created_at >= :start_date AND created_at < :end_date", {start_date: start_date, end_date: end_date}).order(created_at: :asc)
-    invoices.each do |i|
-      i.update_columns(reference: "#{year.to_s[2..3]}#{'%02d' % month}#{index.next!}#{i.stp_invoice_id ? '/VL' : ''}")
-      if i.avoir
-        i.avoir.update_columns(reference: "#{year.to_s[2..3]}#{'%02d' % month}#{index.next!}/A")
-      end
-    end
     invoices.each(&:regenerate_invoice_pdf)
     puts "-> Done"
   end