diff --git a/README.md b/README.md
index d226f76..ac655a9 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@ dependencies in `mix.exs`:
 
 ```elixir
 def deps do
-  [{:exquickbooks, "~> 0.4.0"}]
+  [{:exquickbooks, "~> 0.5.0"}]
 end
 ```
 
diff --git a/config/test.exs b/config/test.exs
index 65804eb..5d875e6 100644
--- a/config/test.exs
+++ b/config/test.exs
@@ -1,6 +1,6 @@
 use Mix.Config
 
 config :exquickbooks,
-  backend: ExQuickBooks.MockBackend,
+  backend: ExQuickBooks.Backend.Mock,
   consumer_key: "key",
   consumer_secret: "secret"
diff --git a/lib/exquickbooks/item.ex b/lib/exquickbooks/api/item.ex
similarity index 88%
rename from lib/exquickbooks/item.ex
rename to lib/exquickbooks/api/item.ex
index 867601f..5533f07 100644
--- a/lib/exquickbooks/item.ex
+++ b/lib/exquickbooks/api/item.ex
@@ -1,4 +1,4 @@
-defmodule ExQuickBooks.Item do
+defmodule ExQuickBooks.API.Item do
   @moduledoc """
   Functions for interacting with the Item API.
 
@@ -7,9 +7,9 @@ defmodule ExQuickBooks.Item do
   """
 
   use ExQuickBooks.Endpoint, base_url: ExQuickBooks.accounting_api
-  use ExQuickBooks.JSONEndpoint
+  use ExQuickBooks.Endpoint.JSON
 
-  alias ExQuickBooks.AccessToken
+  alias ExQuickBooks.OAuth.AccessToken
 
   @doc """
   Creates an item.
@@ -40,7 +40,7 @@ defmodule ExQuickBooks.Item do
   Updates and retrieves an item.
 
   The item map must define all of the keys in the full item map returned by
-  `read_item/3`, otherwise the omitted values are set to their default values
+  `read_item/2`, otherwise the omitted values are set to their default values
   or NULL.
   """
   @spec update_item(AccessToken.t, json_map) ::
diff --git a/lib/exquickbooks/preferences.ex b/lib/exquickbooks/api/preferences.ex
similarity index 90%
rename from lib/exquickbooks/preferences.ex
rename to lib/exquickbooks/api/preferences.ex
index 1a1287e..8e433b6 100644
--- a/lib/exquickbooks/preferences.ex
+++ b/lib/exquickbooks/api/preferences.ex
@@ -1,4 +1,4 @@
-defmodule ExQuickBooks.Preferences do
+defmodule ExQuickBooks.API.Preferences do
   @moduledoc """
   Functions for interacting with the Preferences API.
 
@@ -7,9 +7,9 @@ defmodule ExQuickBooks.Preferences do
   """
 
   use ExQuickBooks.Endpoint, base_url: ExQuickBooks.accounting_api
-  use ExQuickBooks.JSONEndpoint
+  use ExQuickBooks.Endpoint.JSON
 
-  alias ExQuickBooks.AccessToken
+  alias ExQuickBooks.OAuth.AccessToken
 
   @doc """
   Retrieves preferences for the realm.
@@ -26,7 +26,7 @@ defmodule ExQuickBooks.Preferences do
   Updates and retrieves preferences for the realm.
 
   This operation performs a full update. The preferences map must define all of
-  the keys in the full preferences map returned by `read_preferences/2`,
+  the keys in the full preferences map returned by `read_preferences/1`,
   otherwise the omitted values are set to their default values or NULL.
   """
   @spec update_preferences(AccessToken.t, json_map) ::
diff --git a/lib/exquickbooks/backend.ex b/lib/exquickbooks/backend.ex
index 869fd5d..9a33b77 100644
--- a/lib/exquickbooks/backend.ex
+++ b/lib/exquickbooks/backend.ex
@@ -1,7 +1,7 @@
 defmodule ExQuickBooks.Backend do
   @moduledoc false
 
-  alias ExQuickBooks.Request
+  alias ExQuickBooks.Backend.Request
   alias HTTPoison.Error
   alias HTTPoison.Response
 
diff --git a/lib/exquickbooks/httpoison_backend.ex b/lib/exquickbooks/backend/httpoison.ex
similarity index 85%
rename from lib/exquickbooks/httpoison_backend.ex
rename to lib/exquickbooks/backend/httpoison.ex
index 30acdfd..b40d6e5 100644
--- a/lib/exquickbooks/httpoison_backend.ex
+++ b/lib/exquickbooks/backend/httpoison.ex
@@ -1,4 +1,4 @@
-defmodule ExQuickBooks.HTTPoisonBackend do
+defmodule ExQuickBooks.Backend.HTTPoison do
   @moduledoc false
   @behaviour ExQuickBooks.Backend
 
diff --git a/test/support/mock_backend.ex b/lib/exquickbooks/backend/mock.ex
similarity index 95%
rename from test/support/mock_backend.ex
rename to lib/exquickbooks/backend/mock.ex
index 0953f21..fdda747 100644
--- a/test/support/mock_backend.ex
+++ b/lib/exquickbooks/backend/mock.ex
@@ -1,4 +1,4 @@
-defmodule ExQuickBooks.MockBackend do
+defmodule ExQuickBooks.Backend.Mock do
   @moduledoc false
   @behaviour ExQuickBooks.Backend
 
diff --git a/lib/exquickbooks/json_endpoint.ex b/lib/exquickbooks/endpoint/json.ex
similarity index 97%
rename from lib/exquickbooks/json_endpoint.ex
rename to lib/exquickbooks/endpoint/json.ex
index 71c9f79..675540c 100644
--- a/lib/exquickbooks/json_endpoint.ex
+++ b/lib/exquickbooks/endpoint/json.ex
@@ -1,4 +1,4 @@
-defmodule ExQuickBooks.JSONEndpoint do
+defmodule ExQuickBooks.Endpoint.JSON do
   @moduledoc false
 
   import ExQuickBooks.Endpoint, only: [
diff --git a/lib/exquickbooks/oauth.ex b/lib/exquickbooks/oauth.ex
index 2b9583d..2499354 100644
--- a/lib/exquickbooks/oauth.ex
+++ b/lib/exquickbooks/oauth.ex
@@ -15,8 +15,8 @@ defmodule ExQuickBooks.OAuth do
   {:ok, request_token} = ExQuickBooks.get_request_token(callback_url)
   ```
 
-  The token is an `ExQuickBooks.RequestToken`, see its documentation for more
-  details.
+  The token is an `ExQuickBooks.OAuth.RequestToken`, see its documentation for
+  more details.
 
   You should redirect the user to `request_token.redirect_url` to authorise
   your application to access their QuickBooks data. After that step they are
@@ -48,14 +48,14 @@ defmodule ExQuickBooks.OAuth do
   ```
 
   Now you can store the access token and use it in API calls to authenticate on
-  behalf of the user. The token is an `ExQuickBooks.AccessToken`, see its
+  behalf of the user. The token is an `ExQuickBooks.OAuth.AccessToken`, see its
   documentation for more details.
   """
 
   use ExQuickBooks.Endpoint, base_url: ExQuickBooks.oauth_api
 
-  alias ExQuickBooks.AccessToken
-  alias ExQuickBooks.RequestToken
+  alias ExQuickBooks.OAuth.AccessToken
+  alias ExQuickBooks.OAuth.RequestToken
 
   @doc """
   Retrieves a new request token.
diff --git a/lib/exquickbooks/access_token.ex b/lib/exquickbooks/oauth/access_token.ex
similarity index 95%
rename from lib/exquickbooks/access_token.ex
rename to lib/exquickbooks/oauth/access_token.ex
index 0e46abe..b31c8a8 100644
--- a/lib/exquickbooks/access_token.ex
+++ b/lib/exquickbooks/oauth/access_token.ex
@@ -1,4 +1,4 @@
-defmodule ExQuickBooks.AccessToken do
+defmodule ExQuickBooks.OAuth.AccessToken do
   @moduledoc """
   OAuth 1.0a token/secret pair for authenticating API calls.
 
diff --git a/lib/exquickbooks/request_token.ex b/lib/exquickbooks/oauth/request_token.ex
similarity index 95%
rename from lib/exquickbooks/request_token.ex
rename to lib/exquickbooks/oauth/request_token.ex
index e1a61bb..82aa60c 100644
--- a/lib/exquickbooks/request_token.ex
+++ b/lib/exquickbooks/oauth/request_token.ex
@@ -1,4 +1,4 @@
-defmodule ExQuickBooks.RequestToken do
+defmodule ExQuickBooks.OAuth.RequestToken do
   @moduledoc """
   OAuth 1.0a token/secret pair for requesting an access token.
 
diff --git a/mix.exs b/mix.exs
index 21d31ab..8150320 100644
--- a/mix.exs
+++ b/mix.exs
@@ -3,7 +3,7 @@ defmodule ExQuickBooks.Mixfile do
 
   def project do
     [app: :exquickbooks,
-     version: "0.4.0",
+     version: "0.5.0",
      elixir: "~> 1.4",
 
      # Compilation
diff --git a/test/exquickbooks/item_test.exs b/test/exquickbooks/api/item_test.exs
similarity index 94%
rename from test/exquickbooks/item_test.exs
rename to test/exquickbooks/api/item_test.exs
index 5699186..522727e 100644
--- a/test/exquickbooks/item_test.exs
+++ b/test/exquickbooks/api/item_test.exs
@@ -1,9 +1,9 @@
-defmodule ExQuickBooks.ItemTest do
+defmodule ExQuickBooks.API.ItemTest do
   use ExUnit.Case, async: false
   use ExQuickBooks.APICase
 
-  alias ExQuickBooks.AccessToken
-  alias ExQuickBooks.Item
+  alias ExQuickBooks.API.Item
+  alias ExQuickBooks.OAuth.AccessToken
 
   doctest Item
 
diff --git a/test/exquickbooks/preferences_test.exs b/test/exquickbooks/api/preferences_test.exs
similarity index 89%
rename from test/exquickbooks/preferences_test.exs
rename to test/exquickbooks/api/preferences_test.exs
index 8c1f461..5df57bb 100644
--- a/test/exquickbooks/preferences_test.exs
+++ b/test/exquickbooks/api/preferences_test.exs
@@ -1,9 +1,9 @@
-defmodule ExQuickBooks.PreferencesTest do
+defmodule ExQuickBooks.API.PreferencesTest do
   use ExUnit.Case, async: false
   use ExQuickBooks.APICase
 
-  alias ExQuickBooks.AccessToken
-  alias ExQuickBooks.Preferences
+  alias ExQuickBooks.API.Preferences
+  alias ExQuickBooks.OAuth.AccessToken
 
   doctest Preferences
 
diff --git a/test/exquickbooks/json_endpoint_test.exs b/test/exquickbooks/endpoint/json_endpoint_test.exs
similarity index 94%
rename from test/exquickbooks/json_endpoint_test.exs
rename to test/exquickbooks/endpoint/json_endpoint_test.exs
index 4666ce9..3d2e8d1 100644
--- a/test/exquickbooks/json_endpoint_test.exs
+++ b/test/exquickbooks/endpoint/json_endpoint_test.exs
@@ -1,10 +1,10 @@
-defmodule ExQuickBooks.JSONEndpointTest do
+defmodule ExQuickBooks.Endpoint.JSONTest do
   use ExUnit.Case, async: false
   use ExQuickBooks.APICase
   use ExQuickBooks.Endpoint, base_url: "http://localhost/"
-  use ExQuickBooks.JSONEndpoint
+  use ExQuickBooks.Endpoint.JSON
 
-  doctest ExQuickBooks.JSONEndpoint
+  doctest ExQuickBooks.Endpoint.JSON
 
   test "send_json_request/1 sets appropriate headers" do
     request(:get, "path") |> send_json_request
diff --git a/test/exquickbooks/endpoint_test.exs b/test/exquickbooks/endpoint_test.exs
index 5635b74..741d6f0 100644
--- a/test/exquickbooks/endpoint_test.exs
+++ b/test/exquickbooks/endpoint_test.exs
@@ -3,7 +3,7 @@ defmodule ExQuickBooks.EndpointTest do
   use ExQuickBooks.APICase
   use ExQuickBooks.Endpoint, base_url: "http://localhost/"
 
-  alias ExQuickBooks.AccessToken
+  alias ExQuickBooks.OAuth.AccessToken
   alias ExQuickBooks.Request
 
   doctest ExQuickBooks.Endpoint
diff --git a/test/exquickbooks/oauth_test.exs b/test/exquickbooks/oauth_test.exs
index bac2216..b39bbeb 100644
--- a/test/exquickbooks/oauth_test.exs
+++ b/test/exquickbooks/oauth_test.exs
@@ -2,9 +2,9 @@ defmodule ExQuickBooks.OAuthTest do
   use ExUnit.Case, async: false
   use ExQuickBooks.APICase
 
-  alias ExQuickBooks.AccessToken
   alias ExQuickBooks.OAuth
-  alias ExQuickBooks.RequestToken
+  alias ExQuickBooks.OAuth.AccessToken
+  alias ExQuickBooks.OAuth.RequestToken
 
   doctest OAuth
 
diff --git a/test/support/api_case.ex b/test/support/api_case.ex
index df9c337..7a88f31 100644
--- a/test/support/api_case.ex
+++ b/test/support/api_case.ex
@@ -5,7 +5,7 @@ defmodule ExQuickBooks.APICase do
     end
   end
 
-  alias ExQuickBooks.MockBackend
+  alias ExQuickBooks.Backend
   alias HTTPoison.Response
 
   def http_200_response do
@@ -43,8 +43,8 @@ defmodule ExQuickBooks.APICase do
     }
   end
 
-  defdelegate take_request, to: MockBackend
-  defdelegate send_response(response), to: MockBackend
+  defdelegate take_request, to: Backend.Mock
+  defdelegate send_response(response), to: Backend.Mock
 
   defp type_for_extension("json"),  do: "application/json"
   defp type_for_extension(_),       do: "text/plain"