Report no tax collected when order zeroed out

3 files changed, 13 insertions, 1 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4fb0a0d..b83f7af 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## master
 
+- Report no tax collected on order when order total zeroed out.
+
 ## v0.11.1
 
 - Avoid sending negative amounts for order totals.
diff --git a/lib/super_good/solidus_taxjar/api_params.rb b/lib/super_good/solidus_taxjar/api_params.rb
index 3d898c3..ca346ff 100644
--- a/lib/super_good/solidus_taxjar/api_params.rb
+++ b/lib/super_good/solidus_taxjar/api_params.rb
@@ -30,7 +30,7 @@ module SuperGood
               transaction_date: order.completed_at.to_formatted_s(:iso8601),
               amount: [order.total - order.additional_tax_total, 0].max,
               shipping: shipping(order),
-              sales_tax: order.additional_tax_total
+              sales_tax: sales_tax(order)
             )
         end
 
@@ -106,6 +106,12 @@ module SuperGood
         def shipping(order)
           SuperGood::SolidusTaxJar.shipping_calculator.(order)
         end
+
+        def sales_tax(order)
+          return 0 if order.total.zero?
+
+          order.additional_tax_total
+        end
       end
     end
   end
diff --git a/spec/super_good/solidus_taxjar/api_params_spec.rb b/spec/super_good/solidus_taxjar/api_params_spec.rb
index 2e9e289..e16edb9 100644
--- a/spec/super_good/solidus_taxjar/api_params_spec.rb
+++ b/spec/super_good/solidus_taxjar/api_params_spec.rb
@@ -218,6 +218,10 @@ RSpec.describe SuperGood::SolidusTaxJar::APIParams do
       it "sends the order total as zero" do
         expect(subject[:amount]).to be_zero
       end
+
+      it "sends the sales tax total as zero" do
+        expect(subject[:sales_tax]).to be_zero
+      end
     end
 
     context "when the line item has 0 quantity" do