diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index a1f5a733e8..c0bd086700 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -3,7 +3,7 @@ name: Build
 on:
   workflow_dispatch:
   push:
-    branches-ignore:    
+    branches-ignore:
       - 'dependabot/**'
   pull_request:
 
@@ -47,7 +47,7 @@ jobs:
 
       - name: Setup redis
         uses: supercharge/redis-github-action@1.4.0
-        with: 
+        with:
           redis-version: 6
 
       - name: Set up Ruby
@@ -81,11 +81,19 @@ jobs:
           # RSpec split test files by test examples feature - it's optional
           # https://knapsackpro.com/faq/question/how-to-split-slow-rspec-test-files-by-test-examples-by-individual-it
           #KNAPSACK_PRO_RSPEC_SPLIT_BY_TEST_EXAMPLES: true
-          KNAPSACK_PRO_TEST_FILE_PATTERN: "{spec/controllers/**/*_spec.rb}" 
+          KNAPSACK_PRO_TEST_FILE_PATTERN: "{spec/controllers/**/*_spec.rb}"
         run: |
           git show --no-patch # the commit being tested (which is often a merge due to actions/checkout@v3)
           bin/rake knapsack_pro:rspec
 
+      - name: Save SimpleCov file
+        uses: actions/upload-artifact@v3
+        with:
+          name: simplecov-chunk-controllers-${{ matrix.ci_node_index }}
+          path: coverage/*.*
+          retention-days: 2 # doesn't need to be long, because it's the combined results that matter
+          if-no-files-found: ignore
+
   models:
     runs-on: ubuntu-22.04
     services:
@@ -116,7 +124,7 @@ jobs:
 
       - name: Setup redis
         uses: supercharge/redis-github-action@1.4.0
-        with: 
+        with:
           redis-version: 6
 
       - name: Set up Ruby
@@ -141,10 +149,18 @@ jobs:
           # RSpec split test files by test examples feature - it's optional
           # https://knapsackpro.com/faq/question/how-to-split-slow-rspec-test-files-by-test-examples-by-individual-it
           #KNAPSACK_PRO_RSPEC_SPLIT_BY_TEST_EXAMPLES: true
-          KNAPSACK_PRO_TEST_FILE_PATTERN: "{spec/models/**/*_spec.rb}" 
+          KNAPSACK_PRO_TEST_FILE_PATTERN: "{spec/models/**/*_spec.rb}"
         run: |
           bin/rake knapsack_pro:rspec
 
+      - name: Save SimpleCov file
+        uses: actions/upload-artifact@v3
+        with:
+          name: simplecov-chunk-models-${{ matrix.ci_node_index }}
+          path: coverage/*.*
+          retention-days: 2 # doesn't need to be long, because it's the combined results that matter
+          if-no-files-found: ignore
+
   system_admin:
     runs-on: ubuntu-22.04
     services:
@@ -175,7 +191,7 @@ jobs:
 
       - name: Setup redis
         uses: supercharge/redis-github-action@1.4.0
-        with: 
+        with:
           redis-version: 6
 
       - name: Set up Ruby
@@ -209,11 +225,19 @@ jobs:
           # RSpec split test files by test examples feature - it's optional
           # https://knapsackpro.com/faq/question/how-to-split-slow-rspec-test-files-by-test-examples-by-individual-it
           #KNAPSACK_PRO_RSPEC_SPLIT_BY_TEST_EXAMPLES: true
-          KNAPSACK_PRO_TEST_FILE_PATTERN: "{spec/system/admin/**/*_spec.rb}" 
+          KNAPSACK_PRO_TEST_FILE_PATTERN: "{spec/system/admin/**/*_spec.rb}"
 
         run: |
           bin/rake knapsack_pro:queue:rspec
 
+      - name: Save SimpleCov file
+        uses: actions/upload-artifact@v3
+        with:
+          name: simplecov-chunk-system-admin-${{ matrix.ci_node_index }}
+          path: coverage/*.*
+          retention-days: 2 # doesn't need to be long, because it's the combined results that matter
+          if-no-files-found: ignore
+
       - name: Archive failed tests screenshots
         if: failure()
         uses: actions/upload-artifact@v4
@@ -247,13 +271,13 @@ jobs:
         ci_node_total: [12]
         # Indexes for parallel jobs (starting from zero).
         # E.g. use [0, 1] for 2 parallel jobs, [0, 1, 2] for 3 parallel jobs, etc.
-        ci_node_index: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11] 
+        ci_node_index: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
     steps:
       - uses: actions/checkout@v3
 
       - name: Setup redis
         uses: supercharge/redis-github-action@1.4.0
-        with: 
+        with:
           redis-version: 6
 
       - name: Set up Ruby
@@ -287,11 +311,19 @@ jobs:
           # RSpec split test files by test examples feature - it's optional
           # https://knapsackpro.com/faq/question/how-to-split-slow-rspec-test-files-by-test-examples-by-individual-it
           #KNAPSACK_PRO_RSPEC_SPLIT_BY_TEST_EXAMPLES: true
-          KNAPSACK_PRO_TEST_FILE_PATTERN: "{spec/system/consumer/**/*_spec.rb}" 
+          KNAPSACK_PRO_TEST_FILE_PATTERN: "{spec/system/consumer/**/*_spec.rb}"
 
         run: |
           bin/rake knapsack_pro:queue:rspec
 
+      - name: Save SimpleCov file
+        uses: actions/upload-artifact@v3
+        with:
+          name: simplecov-chunk-system-consumer-${{ matrix.ci_node_index }}
+          path: coverage/*.*
+          retention-days: 2 # doesn't need to be long, because it's the combined results that matter
+          if-no-files-found: ignore
+
       - name: Archive failed tests screenshots
         if: failure()
         uses: actions/upload-artifact@v4
@@ -331,7 +363,7 @@ jobs:
 
       - name: Setup redis
         uses: supercharge/redis-github-action@1.4.0
-        with: 
+        with:
           redis-version: 6
 
       - name: Set up Ruby
@@ -371,6 +403,14 @@ jobs:
         run: |
           bin/rake knapsack_pro:rspec
 
+      - name: Save SimpleCov file
+        uses: actions/upload-artifact@v3
+        with:
+          name: simplecov-chunk-engines-${{ matrix.ci_node_index }}
+          path: coverage/*.*
+          retention-days: 2 # doesn't need to be long, because it's the combined results that matter
+          if-no-files-found: ignore
+
   test_the_rest:
     runs-on: ubuntu-22.04
     services:
@@ -401,7 +441,7 @@ jobs:
 
       - name: Setup redis
         uses: supercharge/redis-github-action@1.4.0
-        with: 
+        with:
           redis-version: 6
 
       - name: Set up Ruby
@@ -439,6 +479,14 @@ jobs:
         run: |
           bin/rake knapsack_pro:rspec
 
+      - name: Save SimpleCov file
+        uses: actions/upload-artifact@v3
+        with:
+          name: simplecov-chunk-the-rest-${{ matrix.ci_node_index }}
+          path: coverage/*.*
+          retention-days: 2 # doesn't need to be long, because it's the combined results that matter
+          if-no-files-found: ignore
+
   non_knapsack_jest_karma:
     runs-on: ubuntu-22.04
     services:
@@ -476,3 +524,38 @@ jobs:
 
       - name: Run jest tests
         run: yarn jest
+
+  collate_simplecov_results:
+    runs-on: ubuntu-22.04
+    needs:
+      - controllers
+      - models
+      - engines
+      - system_admin
+      - system_consumer
+      - test_the_rest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true # runs 'bundle install' and caches installed gems automatically
+
+      - name: Download individual results from individual runners
+        uses: actions/download-artifact@v3
+        with:
+          pattern: simplecov-chunk-*
+          path: tmp/simplecov
+          merge-multiple: true
+
+      - name: collate results from each of the workers
+        run: bundle exec rake 'simplecov:collate_results[tmp/simplecov]'
+
+      - name: Upload collated results
+        uses: actions/upload-artifact@v3
+        with:
+          name: combined-simplecov-report
+          path: coverage/*.*
+          retention-days: 7
+          if-no-files-found: ignore
diff --git a/.simplecov b/.simplecov
index 0094b3ddcd..8cf02c6b54 100755
--- a/.simplecov
+++ b/.simplecov
@@ -14,4 +14,6 @@ SimpleCov.start 'rails' do
   add_filter '/log'
   add_filter '/db'
   add_filter '/lib/tasks/sample_data/'
+
+  formatter SimpleCov::Formatter::SimpleFormatter
 end
diff --git a/lib/tasks/simplecov.rake b/lib/tasks/simplecov.rake
new file mode 100644
index 0000000000..b0c896ecb7
--- /dev/null
+++ b/lib/tasks/simplecov.rake
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+namespace :simplecov do
+  desc "Collates all result sets produced during parallel test runs"
+  task :collate_results, # rubocop:disable Rails/RakeEnvironment doesn't need the full env
+       [:path_to_results, :coverage_dir] do |_t, args|
+    require "simplecov"
+
+    path_to_results = args[:path_to_results].presence || "tmp/simplecov"
+    output_path = args[:coverage_dir].presence || "coverage"
+
+    SimpleCov.collate Dir[File.join(path_to_results, "**", ".resultset.json")], "rails" do
+      formatter(SimpleCov::Formatter::HTMLFormatter)
+      coverage_dir(output_path)
+    end
+  end
+end
diff --git a/spec/base_spec_helper.rb b/spec/base_spec_helper.rb
index b56cb83492..5579890b64 100644
--- a/spec/base_spec_helper.rb
+++ b/spec/base_spec_helper.rb
@@ -4,8 +4,9 @@
 
 ENV["RAILS_ENV"] ||= 'test'
 
+# for full configuration, see .simplecov
 require 'simplecov' if ENV["COVERAGE"]
-require 'rubygems'
+
 require 'pry' unless ENV['CI']
 require 'view_component/test_helpers'
 
@@ -27,6 +28,12 @@ end
 require 'knapsack_pro'
 KnapsackPro::Adapters::RSpecAdapter.bind
 
+if ENV["COVERAGE"] && defined?(SimpleCov)
+  KnapsackPro::Hooks::Queue.before_queue do
+    SimpleCov.command_name("rspec_ci_node_#{KnapsackPro::Config::Env.ci_node_index}")
+  end
+end
+
 # Allow connections to selenium whilst raising errors when connecting to external sites
 require 'webmock/rspec'
 WebMock.enable!
diff --git a/spec/fixtures/simplecov/customer/.resultset.json b/spec/fixtures/simplecov/customer/.resultset.json
new file mode 100644
index 0000000000..130cfe0072
--- /dev/null
+++ b/spec/fixtures/simplecov/customer/.resultset.json
@@ -0,0 +1,85 @@
+{
+  "RSpec": {
+    "coverage": {
+      "/Users/josephjohansen/code/open_food_foundation/openfoodnetwork/app/models/customer.rb": {
+        "lines": [
+          null,
+          null,
+          null,
+          null,
+          null,
+          null,
+          null,
+          null,
+          null,
+          1,
+          1,
+          null,
+          1,
+          null,
+          1,
+          null,
+          1,
+          1,
+          1,
+          1,
+          1,
+          1,
+          1,
+          null,
+          1,
+          1,
+          1,
+          null,
+          1,
+          1,
+          1,
+          null,
+          1,
+          1,
+          null,
+          null,
+          null,
+          null,
+          null,
+          8,
+          1,
+          6,
+          null,
+          2,
+          2,
+          null,
+          1,
+          null,
+          1,
+          0,
+          null,
+          null,
+          1,
+          null,
+          1,
+          31,
+          null,
+          null,
+          1,
+          31,
+          null,
+          null,
+          1,
+          24,
+          null,
+          null,
+          1,
+          0,
+          0,
+          0,
+          null,
+          0,
+          null,
+          null
+        ]
+      }
+    },
+    "timestamp": 1724235565
+  }
+}
diff --git a/spec/fixtures/simplecov/voucher/.resultset.json b/spec/fixtures/simplecov/voucher/.resultset.json
new file mode 100644
index 0000000000..db9d793e0e
--- /dev/null
+++ b/spec/fixtures/simplecov/voucher/.resultset.json
@@ -0,0 +1,68 @@
+{
+  "RSpec": {
+    "coverage": {
+      "/Users/josephjohansen/code/open_food_foundation/openfoodnetwork/app/models/voucher.rb": {
+        "lines": [
+          null,
+          null,
+          1,
+          1,
+          null,
+          1,
+          null,
+          1,
+          null,
+          null,
+          null,
+          1,
+          null,
+          null,
+          null,
+          null,
+          1,
+          null,
+          1,
+          null,
+          1,
+          15,
+          null,
+          null,
+          null,
+          null,
+          null,
+          null,
+          null,
+          null,
+          1,
+          null,
+          3,
+          null,
+          null,
+          null,
+          null,
+          null,
+          null,
+          null,
+          null,
+          3,
+          null,
+          null,
+          null,
+          1,
+          1,
+          null,
+          null,
+          1,
+          1,
+          null,
+          null,
+          1,
+          1,
+          null,
+          null
+        ]
+      }
+    },
+    "timestamp": 1724239602
+  }
+}
diff --git a/spec/lib/tasks/simplecov_spec.rb b/spec/lib/tasks/simplecov_spec.rb
new file mode 100644
index 0000000000..68e9d0bc5e
--- /dev/null
+++ b/spec/lib/tasks/simplecov_spec.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rake'
+
+RSpec.describe "simplecov.rake" do
+  before(:all) do
+    Rake.application.rake_require("tasks/simplecov")
+  end
+
+  describe "simplecov:collate_results" do
+    context "when there are reports to merge" do
+      let(:input_dir) { Rails.root.join("spec/fixtures/simplecov") }
+
+      it "creates a new combined report" do
+        Dir.mktmpdir do |tmp_dir|
+          output_dir = File.join(tmp_dir, "output")
+
+          expect {
+            Rake.application.invoke_task(
+              "simplecov:collate_results[#{input_dir},#{output_dir}]"
+            )
+          }.to change { Dir.exist?(output_dir) }.
+            from(false).
+            to(true).
+
+            and change { File.exist?(File.join(output_dir, "index.html")) }.
+            from(false).
+            to(true)
+        end
+      end
+    end
+  end
+end