always render shipment on the invoice

app/models/invoice/data_presenter.rb

@@ -61,6 +61,12 @@ class Invoice
         }
       end
 
+      if exclude.include? :shipment
+        adjustments.reject! { |a|
+          a.adjustable_type == 'Spree::Shipment'
+        }
+      end
+
       if reject_zero_amount
         adjustments.reject! { |a| a.amount == 0 }
       end
@@ -68,6 +74,30 @@ class Invoice
       adjustments
     end
 
+    def shipment_adjustment
+      all_eligible_adjustments.find { |a| a.originator.type == 'Spree::ShippingMethod' }
+    end
+
+    # contains limited information about the shipment
+    def shipment
+      shipment_adjustment.adjustable
+    end
+
+    def display_shipment_amount_without_taxes
+      Spree::Money.new(shipment.amount - shipment.included_tax_total, currency:)
+    end
+
+    def display_shipment_amount_with_taxes
+      Spree::Money.new(shipment.amount + shipment.additional_tax_total, currency:)
+    end
+
+    def display_shipment_tax_rates
+      all_eligible_adjustments.select { |a|
+        a.originator.type == 'Spree::TaxRate' && a.adjustable_type == 'Spree::Shipment'
+      }.map(&:originator)
+        .map { |tr| number_to_percentage(tr.amount * 100, precision: 1) }.join(", ")
+    end
+
     def display_checkout_taxes_hash
       tax_adjustment_totals.map do |tax_rate_id, tax_amount|
         tax_rate = tax_rate_by_id[tax_rate_id]

app/views/spree/admin/orders/_invoice_table4.html.haml

@@ -35,8 +35,20 @@
           = item.display_line_item_tax_rates
         %td{:align => "right"}
           = item.display_amount_with_adjustments_and_with_taxes
-
-    - @order.checkout_adjustments(exclude: [:line_item]).reverse_each do |adjustment|
+    %tr
+      %td
+        %strong= "#{t(:shipping)} "
+        = "( #{t(:invoice_shipping_type)} #{raw(@order.shipping_method.name)} )"
+      %td{:align => "right"}
+      %td{:align => "right"}
+      %td{:align => "right"}
+      %td{:align => "right"}
+        = @order.display_shipment_amount_without_taxes
+      %td{:align => "right"}
+        = @order.display_shipment_tax_rates
+      %td{:align => "right"}
+        = @order.display_shipment_amount_with_taxes
+    - @order.checkout_adjustments(exclude: [:line_item, :shipment]).reverse_each do |adjustment|
       %tr
         %td
           %strong= "#{raw(adjustment.label)}"

config/locales/en.yml

@@ -1885,6 +1885,7 @@ en:
   invoice_tax_total: "GST Total:"
   tax_invoice: "TAX INVOICE"
   tax_total: "Total tax (%{rate}):"
+  invoice_shipping_type: "Type:"
   total_excl_tax: "Total (Excl. tax):"
   total_incl_tax: "Total (Incl. tax):"
   abn: "ABN:"