From f4ae615a3eba9f1dc058c2c374c95dbb5a0fd423 Mon Sep 17 00:00:00 2001
From: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>
Date: Wed, 13 Aug 2025 21:06:19 +0200
Subject: [PATCH] fix(tax): Use correct rule reference for shipping (#13195)

* fix(tax): Use correct rule reference

* fix tests
---
 .../http/__tests__/cart/store/cart.spec.ts    | 60 ++++++++++++++++-
 .../integration-tests/__tests__/index.spec.ts | 64 ++++++++++++++++++-
 .../tax/src/services/tax-module-service.ts    |  2 +-
 3 files changed, 122 insertions(+), 4 deletions(-)

diff --git a/integration-tests/http/__tests__/cart/store/cart.spec.ts b/integration-tests/http/__tests__/cart/store/cart.spec.ts
index 54c3f8c6c2..731e6d3376 100644
--- a/integration-tests/http/__tests__/cart/store/cart.spec.ts
+++ b/integration-tests/http/__tests__/cart/store/cart.spec.ts
@@ -45,7 +45,8 @@ medusaIntegrationTestRunner({
         cart,
         customer,
         promotion,
-        shippingProfile
+        shippingProfile,
+        taxSeedData
 
       beforeAll(async () => {
         appContainer = getContainer()
@@ -78,7 +79,7 @@ medusaIntegrationTestRunner({
           )
         ).data.shipping_profile
 
-        await setupTaxStructure(appContainer.resolve(Modules.TAX))
+        taxSeedData = await setupTaxStructure(appContainer.resolve(Modules.TAX))
 
         region = (
           await api.post(
@@ -4173,6 +4174,61 @@ medusaIntegrationTestRunner({
           )
         })
 
+        it("should add shipping method with tax rate override to cart", async () => {
+          let taxRegion = (
+            await api.get(`/admin/tax-regions?country_code=us`, adminHeaders)
+          ).data.tax_regions[0]
+
+          // Create tax rate override for shipping option
+          await api.post(
+            `/admin/tax-rates`,
+            {
+              name: "Shipping Option Override",
+              tax_region_id: taxRegion.id,
+              rate: 25,
+              code: "T25",
+              is_combinable: false,
+              rules: [
+                {
+                  reference: "shipping_option",
+                  reference_id: shippingOption.id,
+                },
+              ],
+              is_default: false,
+            },
+            adminHeaders
+          )
+
+          let response = await api.post(
+            `/store/carts/${cart.id}/shipping-methods`,
+            { option_id: shippingOption.id },
+            storeHeaders
+          )
+
+          expect(response.status).toEqual(200)
+          expect(response.data.cart).toEqual(
+            expect.objectContaining({
+              id: cart.id,
+              shipping_methods: expect.arrayContaining([
+                expect.objectContaining({
+                  shipping_option_id: shippingOption.id,
+                  amount: 1000,
+                  is_tax_inclusive: true,
+                  tax_lines: expect.arrayContaining([
+                    expect.objectContaining({
+                      id: expect.any(String),
+                      description: "Shipping Option Override",
+                      code: "T25",
+                      rate: 25,
+                      provider_id: "system",
+                    }),
+                  ]),
+                }),
+              ]),
+            })
+          )
+        })
+
         it("should throw when prices are not setup for shipping option", async () => {
           cart = (
             await api.post(
diff --git a/packages/modules/tax/integration-tests/__tests__/index.spec.ts b/packages/modules/tax/integration-tests/__tests__/index.spec.ts
index beeea521fc..87eb559c5f 100644
--- a/packages/modules/tax/integration-tests/__tests__/index.spec.ts
+++ b/packages/modules/tax/integration-tests/__tests__/index.spec.ts
@@ -1,7 +1,7 @@
 import { ITaxModuleService } from "@medusajs/framework/types"
 import { Module, Modules, toMikroORMEntity } from "@medusajs/framework/utils"
-import { TaxModuleService } from "@services"
 import { moduleIntegrationTestRunner } from "@medusajs/test-utils"
+import { TaxModuleService } from "@services"
 import { setupTaxStructure } from "../utils/setup-tax-structure"
 
 jest.setTimeout(30000)
@@ -717,6 +717,68 @@ moduleIntegrationTestRunner<ITaxModuleService>({
         ])
       })
 
+      it("prioritizes specific shipping rate over default rate", async () => {
+        const region = await service.createTaxRegions({
+          country_code: "US",
+          provider_id: "tp_system",
+          default_tax_rate: {
+            code: "TEST",
+            name: "Test Rate",
+            rate: 5,
+          },
+        })
+
+        const rate = await service.createTaxRates({
+          tax_region_id: region.id,
+          name: "Shipping Rate",
+          code: "SHIPPING_TEST",
+          rate: 2,
+        })
+
+        const item = {
+          id: "shipping_test",
+          shipping_option_id: "so_1234",
+          quantity: 1,
+        }
+
+        const calculationContext = {
+          address: {
+            country_code: "US",
+          },
+        }
+
+        let taxLines = await service.getTaxLines([item], calculationContext)
+
+        expect(taxLines).toEqual([
+          expect.objectContaining({
+            rate_id: expect.any(String),
+            rate: 5,
+            code: "TEST",
+            name: "Test Rate",
+          }),
+        ])
+
+        await service.updateTaxRates(rate.id, {
+          rules: [
+            {
+              reference: "shipping_option",
+              reference_id: "so_1234",
+            },
+          ],
+        })
+
+        taxLines = await service.getTaxLines([item], calculationContext)
+
+        expect(taxLines).toEqual([
+          expect.objectContaining({
+            rate_id: expect.any(String),
+            rate: 2,
+            code: "SHIPPING_TEST",
+            name: "Shipping Rate",
+          }),
+        ])
+      })
+
       it("should delete tax rate", async () => {
         const region = await service.createTaxRegions({
           country_code: "US",
diff --git a/packages/modules/tax/src/services/tax-module-service.ts b/packages/modules/tax/src/services/tax-module-service.ts
index 3c75b356bf..6971e9dc75 100644
--- a/packages/modules/tax/src/services/tax-module-service.ts
+++ b/packages/modules/tax/src/services/tax-module-service.ts
@@ -654,7 +654,7 @@ export default class TaxModuleService
     const matchingRules = rate.rules.filter((rule) => {
       if (isShipping) {
         return (
-          rule.reference === "shipping" &&
+          rule.reference === "shipping_option" &&
           rule.reference_id === item.shipping_option_id
         )
       }