diff --git a/app/models/spree/tax_rate_decorator.rb b/app/models/spree/tax_rate_decorator.rb
index 652fb5b62b..a053394dbf 100644
--- a/app/models/spree/tax_rate_decorator.rb
+++ b/app/models/spree/tax_rate_decorator.rb
@@ -8,19 +8,18 @@ module Spree
       alias_method_chain :match, :sales_tax_registration
     end
 
-
     def adjust_with_included_tax(order)
       adjust_without_included_tax(order)
 
       order.adjustments(:reload)
       order.line_items(:reload)
-      (order.adjustments.tax + order.price_adjustments).each do |a|
-        a.set_absolute_included_tax! a.amount
+      # TaxRate adjustments (order.adjustments.tax) and price adjustments (tax included on line items) consist of 100% tax
+      (order.adjustments.tax + order.price_adjustments).each do |adjustment|
+        adjustment.set_absolute_included_tax! adjustment.amount
       end
     end
     alias_method_chain :adjust, :included_tax
 
-
     # Manually apply a TaxRate to a particular amount. TaxRates normally compute against
     # LineItems or Orders, so we mock out a line item here to fit the interface
     # that our calculator (usually DefaultTax) expects.
@@ -40,7 +39,6 @@ module Spree
       end
     end
 
-
     private
 
     def with_tax_included_in_price
diff --git a/config/initializers/spree.rb b/config/initializers/spree.rb
index 83e854a08f..5c60a92778 100644
--- a/config/initializers/spree.rb
+++ b/config/initializers/spree.rb
@@ -7,7 +7,6 @@
 # config.setting_name = 'new value'
 
 require 'spree/product_filters'
-require 'spree/core/calculated_adjustments_decorator'
 
 require "#{Rails.root}/app/models/spree/payment_method_decorator"
 require "#{Rails.root}/app/models/spree/gateway_decorator"
diff --git a/lib/spree/core/calculated_adjustments_decorator.rb b/lib/spree/core/calculated_adjustments_decorator.rb
deleted file mode 100644
index 592bf59854..0000000000
--- a/lib/spree/core/calculated_adjustments_decorator.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-module Spree
-  module Core
-    module CalculatedAdjustments
-      class << self
-        def included_with_explicit_class_name(klass)
-          included_without_explicit_class_name(klass)
-
-          klass.class_eval do
-            has_one :calculator, as: :calculable, dependent: :destroy, class_name: 'Spree::Calculator'
-          end
-        end
-        alias_method_chain :included, :explicit_class_name
-      end
-    end
-  end
-end
diff --git a/spec/factories.rb b/spec/factories.rb
index 280c378c42..e5f785b439 100644
--- a/spec/factories.rb
+++ b/spec/factories.rb
@@ -378,7 +378,7 @@ FactoryBot.define do
         shipping_method { create(:shipping_method) }
       end
       after(:create) do |shipment, evaluator|
-        shipment.shipping_rates.destroy_all # remove existing shipping_rates from shipment
+        shipment.shipping_rates.destroy_all
         shipment.add_shipping_method(evaluator.shipping_method, true)
       end
     end
@@ -390,7 +390,7 @@ FactoryBot.define do
 
       after(:create) do |shipment, evaluator|
         shipping_method = create(:shipping_method_with, :shipping_fee, shipping_fee: evaluator.shipping_fee)
-        shipment.shipping_rates.destroy_all # remove existing shipping_rates from shipment
+        shipment.shipping_rates.destroy_all
         shipment.add_shipping_method(shipping_method, true)
       end
     end
diff --git a/spec/models/spree/adjustment_spec.rb b/spec/models/spree/adjustment_spec.rb
index 1771078cfb..06bbdc9274 100644
--- a/spec/models/spree/adjustment_spec.rb
+++ b/spec/models/spree/adjustment_spec.rb
@@ -61,38 +61,43 @@ module Spree
       describe "Shipment adjustments" do
         let(:shipping_method) { create(:shipping_method_with, :flat_rate) }
         let(:shipment)        { create(:shipment_with, :shipping_method, shipping_method: shipping_method) }
-        let!(:order)          { create(:order, distributor: hub, shipments: [shipment]) }
+        let(:order)           { create(:order, distributor: hub) }
         let(:hub)             { create(:distributor_enterprise, charges_sales_tax: true) }
-        let!(:line_item)      { create(:line_item, order: order) }
+        let(:line_item)       { create(:line_item, order: order) }
         let(:adjustment)      { order.adjustments(:reload).shipping.first }
 
-        it "has a shipping charge of $50" do
-          adjustment.amount.should == 50
+        describe "the shipping charge" do
+          it "is the adjustment amount" do
+            order.shipments = [shipment]
+
+            adjustment.amount.should == 50
+          end
         end
 
         describe "when tax on shipping is disabled" do
+          before { Config.shipment_inc_vat = false }
           it "records 0% tax on shipment adjustments" do
-            Config.shipment_inc_vat = false
             Config.shipping_tax_rate = 0
+            order.shipments = [shipment]
 
             adjustment.included_tax.should == 0
           end
 
           it "records 0% tax on shipments when a rate is set but shipment_inc_vat is false" do
-            Config.shipment_inc_vat = false
             Config.shipping_tax_rate = 0.25
+            order.shipments = [shipment]
 
             adjustment.included_tax.should == 0
           end
         end
 
         describe "when tax on shipping is enabled" do
-          before do
-            Config.shipment_inc_vat = true
-            Config.shipping_tax_rate = 0.25
-          end
+        before { Config.shipment_inc_vat = true }
 
           it "takes the shipment adjustment tax included from the system setting" do
+            Config.shipping_tax_rate = 0.25
+            order.shipments = [shipment]
+
             # Finding the tax included in an amount that's already inclusive of tax:
             # total - ( total / (1 + rate) )
             # 50    - ( 50    / (1 + 0.25) )
@@ -101,14 +106,15 @@ module Spree
           end
 
           it "records 0% tax on shipments when shipping_tax_rate is not set" do
-            Config.shipment_inc_vat = true
             Config.shipping_tax_rate = nil
+            order.shipments = [shipment]
 
             adjustment.included_tax.should == 0
           end
 
           it "records 0% tax on shipments when the distributor does not charge sales tax" do
             order.distributor.update_attributes! charges_sales_tax: false
+            order.shipments = [shipment]
 
             adjustment.included_tax.should == 0
           end