diff --git a/app/uat_actions/uat_actions/generate_fluidx_barcodes.rb b/app/uat_actions/uat_actions/generate_fluidx_barcodes.rb
new file mode 100644
index 0000000000..df895c7ab0
--- /dev/null
+++ b/app/uat_actions/uat_actions/generate_fluidx_barcodes.rb
@@ -0,0 +1,153 @@
+# frozen_string_literal: true
+
+# UAT action to generate randomised FluidX barcodes in the following format:
+# <prefix><random><suffix>: Ten characters in total
+#   <prefix>: two uppercase letters
+#   <random>: six random digits; may be truncated from the end to fit the length
+#   <suffix>: <zero><index>
+#     <zero>: one digit that separates random part and index, i.e. '0'
+#     <index>: sequential tail, 1 to 3 digits, e.g., '9', '99', and '999'
+#
+# Sequential tail in barcodes may be higher and may have gaps because of
+# handling duplicates.
+# Random part may be truncated from right to fit the length of the barcode.
+class UatActions::GenerateFluidxBarcodes < UatActions
+  class_attribute :max_number_of_iterations
+  self.title = 'Generate FluidX Barcodes'
+  self.description = 'Generate randomised FluidX barcodes'
+  self.category = :auxiliary_data
+  self.max_number_of_iterations = 10
+
+  validates :barcode_count,
+            presence: true,
+            numericality: {
+              only_integer: true,
+              greater_than: 0,
+              less_than_or_equal_to: 96
+            }
+  validates :barcode_prefix,
+            presence: true,
+            length: {
+              is: 2
+            },
+            format: {
+              with: /\A[A-Z]{2}\z/,
+              message: 'only allows two uppercase letters'
+            }
+  validates :barcode_index,
+            presence: true,
+            numericality: {
+              only_integer: true,
+              greater_than: 0,
+              less_than_or_equal_to: 900
+            }
+
+  form_field :barcode_count,
+             :number_field,
+             label: 'Number of barcodes',
+             help: 'The number of FluidX barcodes that should be generated',
+             options: {
+               min: 1,
+               max: 96,
+               value: 1
+             }
+  form_field :barcode_prefix,
+             :text_field,
+             label: 'Barcode prefix',
+             help: 'The prefix to be used for the barcodes',
+             options: {
+               maxlength: 2,
+               oninput: 'javascript:this.value=this.value.toUpperCase().replace(/[^A-Z]/g, "")',
+               value: 'TS'
+             }
+  form_field :barcode_index,
+             :number_field,
+             label: 'Barcode index',
+             help: 'The starting index to make a sequential tail for the barcodes',
+             options: {
+               min: 1,
+               max: 900,
+               value: 1
+             }
+
+  # This method is called from the save method after validations have passed.
+  # If the return value is true, the report hash populated by the action is
+  # used for rendering the response. If the return value is false, the errors
+  # collection is used.
+  #
+  # @return [Boolean] true if the action was successful; false otherwise
+  def perform
+    random = generate_random
+    barcodes = generate_barcodes(barcode_count.to_i, barcode_prefix, random, barcode_index.to_i)
+    if barcodes.size == barcode_count.to_i
+      report['barcodes'] = barcodes
+      true
+    else
+      errors.add(:base, 'Failed to generate unique barcodes')
+      false
+    end
+  end
+
+  # Returns a default copy of the UatAction which will be used to fill in the form.
+  #
+  # @return [UatActions::GenerateFluidxBarcodes] a default object for rendering a form
+  def self.default
+    new(barcode_count: '1', barcode_prefix: 'TS', barcode_index: '1')
+  end
+
+  private
+
+  # Generates a random string of six digits. Each digit is randomised separately
+  # for uniform distribution of digits because the string may be truncated later
+  # to fit the barcode_index.
+  #
+  # @return [String] a random string of six digits
+  def generate_random
+    Array.new(6) { rand(0..9) }.join # uniform distribution of digits
+  end
+
+  # Generates an array of barcodes with the specified count, prefix, random
+  # part, and starting index for the sequential tail. It attempts to generate
+  # unique barcodes, iterating up to max_number_of_iterations before giving up.
+  #
+  # @param count [Integer] the number of barcodes to generate
+  # @param prefix [String] the prefix to be used for the barcodes
+  # @param random [String] random part for the barcodes
+  # @param index [Integer] the starting index for the sequential tail
+  # @return [Array<String>] an array of unique barcodes
+  def generate_barcodes(count, prefix, random, index)
+    barcodes = []
+    max_number_of_iterations.times do
+      # Filter out the barcodes that already exist in the database and make sure
+      # there is no duplication in the generated barcodes.
+      barcodes.concat(filter_barcodes(build_barcodes(count, prefix, random, index))).uniq!
+      return barcodes if barcodes.size == barcode_count.to_i
+      count = barcode_count.to_i - barcodes.size # More to generate.
+      index += barcode_count.to_i # Continue index.
+    end
+  end
+
+  # Filters out the barcodes that already exist in the database.
+  #
+  # @param barcodes [Array<String>] an array of barcodes
+  # @return [Array<String>] an array of unique barcodes
+  def filter_barcodes(barcodes)
+    barcodes - Barcode.where(barcode: barcodes).pluck(:barcode)
+  end
+
+  # Builds an array of barcodes with the specified count, prefix, random
+  # part, and starting index for the sequential tail.
+  #
+  # @param count [Integer] the number of barcodes to generate
+  # @param prefix [String] the prefix to be used for the barcodes
+  # @param random [String] random part for the barcodes
+  # @param index [Integer] the starting index for the suffix
+  # @return [Array<String>] an array of barcodes
+  def build_barcodes(count, prefix, random, index)
+    (index...(index + count)).map do |counter|
+      suffix = "0#{counter}"
+      random = random[0, 8 - suffix.length] # 8 FluidX digits minus suffix
+      "#{prefix}#{random}#{suffix}"
+    end
+  end
+end
diff --git a/spec/uat_actions/generate_fluidx_barcodes_spec.rb b/spec/uat_actions/generate_fluidx_barcodes_spec.rb
new file mode 100644
index 0000000000..c3062dd78b
--- /dev/null
+++ b/spec/uat_actions/generate_fluidx_barcodes_spec.rb
@@ -0,0 +1,153 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+# rubocop:disable RSpec/MultipleExpectations
+describe UatActions::GenerateFluidxBarcodes do
+  let(:uat_action) { described_class.new(params) }
+
+  describe '.default' do
+    let(:uat_action) { described_class.default }
+
+    it 'returns a default instance' do
+      expect(uat_action).to be_an_instance_of(described_class)
+      expect(uat_action).to be_valid
+    end
+  end
+
+  describe '#perform' do
+    context 'with default instance' do
+      let(:uat_action) { described_class.default }
+
+      it 'generates barcodes' do
+        expect(uat_action.perform).to be true # Note that this calls the perform method
+        expect(uat_action.report['barcodes'].size).to eq uat_action.barcode_count.to_i
+        expect(uat_action.report['barcodes'].first).to match(/\A[A-Z]{2}\d{8}\z/)
+        expect(uat_action.report['barcodes'].first).to start_with(uat_action.barcode_prefix)
+        expect(uat_action.report['barcodes'].first).to end_with(uat_action.barcode_index.to_s)
+      end
+    end
+
+    context 'with valid options' do
+      let(:params) { { barcode_count: 10, barcode_prefix: 'SQ', barcode_index: 1 } }
+
+      # rubocop:disable RSpec/ExampleLength
+      it 'generates barcodes' do
+        expect(uat_action.perform).to be true
+        expect(uat_action.report['barcodes'].size).to eq params[:barcode_count].to_i
+        expect(uat_action.report['barcodes']).to all(match(/\A[A-Z]{2}\d{8}\z/))
+        expect(uat_action.report['barcodes']).to all(start_with(params[:barcode_prefix]))
+        expect(uat_action.report['barcodes'].first).to end_with(params[:barcode_index].to_s) # first index
+        expect(uat_action.report['barcodes'].last).to end_with(params[:barcode_count].to_s) # last
+      end
+      # rubocop:enable RSpec/ExampleLength
+    end
+
+    context 'with existing barcodes' do
+      let(:params) { { barcode_count: 10, barcode_prefix: 'SQ', barcode_index: 1 } }
+
+      let(:existing_barcodes) do
+        # Create 10 FluidX barcodes: SQ00000001 to SQ00000010
+        (1..10).map { |index| create(:fluidx, barcode: format('SQ%08d', index)).barcode }
+      end
+
+      before do
+        existing_barcodes
+        # Make generated barcodes predictable.
+        allow(uat_action).to receive(:generate_random).and_return('000000')
+      end
+
+      it 'generates unique barcodes' do
+        expect(uat_action.perform).to be true
+        existing_barcodes.each { |existing| expect(uat_action.report['barcodes']).not_to include(existing) }
+      end
+    end
+
+    context 'with max number of iterations' do
+      let(:params) { { barcode_count: 10, barcode_prefix: 'SQ', barcode_index: 1 } }
+
+      before { allow(uat_action).to receive(:filter_barcodes).and_return([]) }
+
+      it 'fails to generate unique barcodes' do
+        expect(uat_action.perform).to be false
+        expect(uat_action.errors[:base]).to include('Failed to generate unique barcodes')
+      end
+    end
+  end
+
+  describe '#valid?' do
+    shared_examples 'an invalid action' do |field, error_message|
+      it "is invalid when #{field} is invalid" do
+        expect(uat_action).not_to be_valid
+        expect(uat_action.errors[field]).to include(error_message)
+      end
+    end
+
+    context 'with barcode_count not present' do
+      let(:params) { { barcode_prefix: 'SQ', barcode_index: 1 } }
+
+      it_behaves_like 'an invalid action', :barcode_count, 'can\'t be blank'
+    end
+
+    context 'with barcode_count non-integer' do
+      let(:params) { { barcode_count: 'not-an-integer', barcode_prefix: 'SQ', barcode_index: 1 } }
+
+      it_behaves_like 'an invalid action', :barcode_count, 'is not a number'
+    end
+
+    context 'with barcode_count smaller than one' do
+      let(:params) { { barcode_count: '0', barcode_prefix: 'SQ', barcode_index: 1 } }
+
+      it_behaves_like 'an invalid action', :barcode_count, 'must be greater than 0'
+    end
+
+    context 'with barcode_count greater than 96' do
+      let(:params) { { barcode_count: '97', barcode_prefix: 'SQ', barcode_index: 1 } }
+
+      it_behaves_like 'an invalid action', :barcode_count, 'must be less than or equal to 96'
+    end
+
+    context 'with barcode_prefix not present' do
+      let(:params) { { barcode_count: '96', barcode_index: 1 } }
+
+      it_behaves_like 'an invalid action', :barcode_prefix, 'can\'t be blank'
+    end
+
+    context 'with barcode_prefix longer than two characters' do
+      let(:params) { { barcode_count: '10', barcode_prefix: 'ABC', barcode_index: 1 } }
+
+      it_behaves_like 'an invalid action', :barcode_prefix, 'is the wrong length (should be 2 characters)'
+    end
+
+    context 'with barcode_prefix not uppercase' do
+      let(:params) { { barcode_count: '10', barcode_prefix: 'bc', barcode_index: 1 } }
+
+      it_behaves_like 'an invalid action', :barcode_prefix, 'only allows two uppercase letters'
+    end
+
+    context 'with barcode_index non present' do
+      let(:params) { { barcode_count: '10', barcode_prefix: 'SQ' } }
+
+      it_behaves_like 'an invalid action', :barcode_index, 'can\'t be blank'
+    end
+
+    context 'with barcode_index non-integer' do
+      let(:params) { { barcode_count: '10', barcode_prefix: 'SQ', barcode_index: 'not-an-integer' } }
+
+      it_behaves_like 'an invalid action', :barcode_index, 'is not a number'
+    end
+
+    context 'with barcode_index smaller than one' do
+      let(:params) { { barcode_count: '10', barcode_prefix: 'SQ', barcode_index: 0 } }
+
+      it_behaves_like 'an invalid action', :barcode_index, 'must be greater than 0'
+    end
+
+    context 'with barcode_count less than 901' do
+      let(:params) { { barcode_count: '10', barcode_prefix: 'SQ', barcode_index: 901 } }
+
+      it_behaves_like 'an invalid action', :barcode_index, 'must be less than or equal to 900'
+    end
+  end
+end
+# rubocop:enable RSpec/MultipleExpectations