diff --git a/lib/avatax/client.rb b/lib/avatax/client.rb
index 0bb64f2..39a83df 100644
--- a/lib/avatax/client.rb
+++ b/lib/avatax/client.rb
@@ -6,6 +6,7 @@ class Client < API
     include AvaTax::Client::Addresses
     include AvaTax::Client::Batches
     include AvaTax::Client::CertExpressInvites
+    include AvaTax::Client::Certificates
     include AvaTax::Client::Companies
     include AvaTax::Client::Contacts
     include AvaTax::Client::Customers