diff --git a/lib/harvest/base.rb b/lib/harvest/base.rb
index 28e0d7d..fe25a7f 100644
--- a/lib/harvest/base.rb
+++ b/lib/harvest/base.rb
@@ -50,6 +50,11 @@ def tasks
       Harvest::Resources::Task
     end
 
+    # Invoices
+    def invoices
+      Harvest::Resources::Invoice
+    end
+
     private
     
       # Configure resource base class so that 
diff --git a/lib/harvest/resources/invoice.rb b/lib/harvest/resources/invoice.rb
new file mode 100644
index 0000000..0b47aa6
--- /dev/null
+++ b/lib/harvest/resources/invoice.rb
@@ -0,0 +1,13 @@
+module Harvest
+  module Resources
+    class Invoice < Harvest::HarvestResource
+      self.element_name = 'invoice'
+
+      class << self
+        def find_by_number number
+          find(find(:all).detect{|i|i.number == number}.id)
+        end
+      end
+    end
+  end
+end