diff --git a/spec/controllers/spree/admin/adjustments_controller_spec.rb b/spec/controllers/spree/admin/adjustments_controller_spec.rb
index b8e1a2bb13..1e6fe5f8a5 100644
--- a/spec/controllers/spree/admin/adjustments_controller_spec.rb
+++ b/spec/controllers/spree/admin/adjustments_controller_spec.rb
@@ -43,71 +43,110 @@ module Spree
       end
     end
 
-    describe "setting included tax" do
+    describe "setting the adjustment's tax" do
       let(:order) { create(:order) }
-      let(:tax_rate) { create(:tax_rate, amount: 0.1, calculator: ::Calculator::DefaultTax.new) }
+      let(:zone) { create(:zone_with_member) }
+      let(:tax_rate) { create(:tax_rate, amount: 0.1, zone: zone, included_in_price: true ) }
 
       describe "creating an adjustment" do
-        it "sets included tax to zero when no tax rate is specified" do
-          spree_post :create, order_id: order.number,
-                              adjustment: { label: 'Testing included tax', amount: '110' }, tax_rate_id: ''
-          expect(response).to redirect_to spree.admin_order_adjustments_path(order)
+        let(:tax_category_param) { '' }
+        let(:params) {
+          {
+            order_id: order.number,
+            adjustment: {
+              label: 'Testing included tax', amount: '110', tax_category_id: tax_category_param
+            }
+          }
+        }
 
-          a = Adjustment.last
-          expect(a.label).to eq('Testing included tax')
-          expect(a.amount).to eq(110)
-          expect(a.included_tax).to eq(0)
-          expect(a.order_id).to eq(order.id)
+        context "when no tax category is specified" do
+          it "doesn't apply tax" do
+            spree_post :create, params
+            expect(response).to redirect_to spree.admin_order_adjustments_path(order)
 
-          expect(order.reload.total).to eq 110
+            new_adjustment = Adjustment.admin.last
+
+            expect(new_adjustment.label).to eq('Testing included tax')
+            expect(new_adjustment.amount).to eq(110)
+            expect(new_adjustment.tax_category).to be_nil
+            expect(new_adjustment.order_id).to eq(order.id)
+
+            expect(order.reload.total).to eq 110
+            expect(order.included_tax_total).to eq 0
+          end
         end
 
-        it "calculates included tax when a tax rate is provided" do
-          spree_post :create, order_id: order.number,
-                              adjustment: { label: 'Testing included tax', amount: '110' }, tax_rate_id: tax_rate.id.to_s
-          expect(response).to redirect_to spree.admin_order_adjustments_path(order)
+        context "when a tax category is provided" do
+          let(:tax_category_param) { tax_rate.tax_category.id.to_s }
 
-          a = Adjustment.last
-          expect(a.label).to eq('Testing included tax')
-          expect(a.amount).to eq(110)
-          expect(a.included_tax).to eq(10)
-          expect(a.order_id).to eq(order.id)
+          it "applies tax" do
+            spree_post :create, params
+            expect(response).to redirect_to spree.admin_order_adjustments_path(order)
 
-          expect(order.reload.total).to eq 110
+            new_adjustment = Adjustment.admin.last
+
+            expect(new_adjustment.label).to eq('Testing included tax')
+            expect(new_adjustment.amount).to eq(110)
+            expect(new_adjustment.tax_category).to eq tax_rate.tax_category
+            expect(new_adjustment.order_id).to eq(order.id)
+
+            expect(order.reload.total).to eq 110
+            expect(order.included_tax_total).to eq 10
+          end
         end
       end
 
       describe "updating an adjustment" do
+        let(:old_tax_category) { create(:tax_category) }
+        let(:tax_category_param) { '' }
+        let(:params) {
+          {
+            id: adjustment.id,
+            order_id: order.number,
+            adjustment: {
+              label: 'Testing included tax', amount: '110', tax_category_id: tax_category_param
+            }
+          }
+        }
         let(:adjustment) {
-          create(:adjustment, adjustable: order, order: order, amount: 1100, included_tax: 100)
+          create(:adjustment, adjustable: order, order: order,
+                              amount: 1100, tax_category: old_tax_category)
         }
 
-        it "sets included tax to zero when no tax rate is specified" do
-          spree_put :update, order_id: order.number, id: adjustment.id,
-                             adjustment: { label: 'Testing included tax', amount: '110' }, tax_rate_id: ''
-          expect(response).to redirect_to spree.admin_order_adjustments_path(order)
+        context "when no tax category is specified" do
+          it "doesn't apply tax" do
+            spree_put :update, params
+            expect(response).to redirect_to spree.admin_order_adjustments_path(order)
 
-          a = Adjustment.last
-          expect(a.label).to eq('Testing included tax')
-          expect(a.amount).to eq(110)
-          expect(a.included_tax).to eq(0)
-          expect(a.order_id).to eq(order.id)
+            adjustment = Adjustment.admin.last
 
-          expect(order.reload.total).to eq 110
+            expect(adjustment.label).to eq('Testing included tax')
+            expect(adjustment.amount).to eq(110)
+            expect(adjustment.tax_category).to be_nil
+            expect(adjustment.order_id).to eq(order.id)
+
+            expect(order.reload.total).to eq 110
+            expect(order.included_tax_total).to eq 0
+          end
         end
 
-        it "calculates included tax when a tax rate is provided" do
-          spree_put :update, order_id: order.number, id: adjustment.id,
-                             adjustment: { label: 'Testing included tax', amount: '110' }, tax_rate_id: tax_rate.id.to_s
-          expect(response).to redirect_to spree.admin_order_adjustments_path(order)
+        context "when a tax category is provided" do
+          let(:tax_category_param) { tax_rate.tax_category.id.to_s }
 
-          a = Adjustment.last
-          expect(a.label).to eq('Testing included tax')
-          expect(a.amount).to eq(110)
-          expect(a.included_tax).to eq(10)
-          expect(a.order_id).to eq(order.id)
+          it "applies tax" do
+            spree_put :update, params
+            expect(response).to redirect_to spree.admin_order_adjustments_path(order)
 
-          expect(order.reload.total).to eq 110
+            adjustment = Adjustment.admin.last
+
+            expect(adjustment.label).to eq('Testing included tax')
+            expect(adjustment.amount).to eq(110)
+            expect(adjustment.tax_category).to eq tax_rate.tax_category
+            expect(adjustment.order_id).to eq(order.id)
+
+            expect(order.reload.total).to eq 110
+            expect(order.included_tax_total).to eq 10
+          end
         end
       end
     end
@@ -151,7 +190,7 @@ module Spree
       let(:order) { create(:completed_order_with_totals) }
       let(:tax_rate) { create(:tax_rate, amount: 0.1, calculator: ::Calculator::DefaultTax.new) }
       let(:adjustment) {
-        create(:adjustment, adjustable: order, order: order, amount: 1100, included_tax: 100)
+        create(:adjustment, adjustable: order, order: order, amount: 1100)
       }
 
       before do
@@ -161,7 +200,7 @@ module Spree
       it "doesn't create adjustments" do
         expect {
           spree_post :create, order_id: order.number,
-                              adjustment: { label: "Testing", amount: "110" }, tax_rate_id: ""
+                              adjustment: { label: "Testing", amount: "110" }
         }.to_not change { [Adjustment.count, order.reload.total] }
 
         expect(response).to redirect_to spree.admin_order_adjustments_path(order)
@@ -170,7 +209,7 @@ module Spree
       it "doesn't change adjustments" do
         expect {
           spree_put :update, order_id: order.number, id: adjustment.id,
-                             adjustment: { label: "Testing", amount: "110" }, tax_rate_id: ""
+                             adjustment: { label: "Testing", amount: "110" }
         }.to_not change { [adjustment.reload.amount, order.reload.total] }
 
         expect(response).to redirect_to spree.admin_order_adjustments_path(order)