diff --git a/Gemfile b/Gemfile
index ee149950cf..e6fd5c3dac 100644
--- a/Gemfile
+++ b/Gemfile
@@ -88,7 +88,7 @@ gem 'redis', '>= 4.0', require: ['redis', 'redis/connection/hiredis']
 gem 'sidekiq'
 gem 'sidekiq-scheduler'
 
-gem "cable_ready", "5.0.0.pre2"
+gem "cable_ready", "5.0.0.pre3"
 
 gem 'combine_pdf'
 gem 'wicked_pdf'
diff --git a/Gemfile.lock b/Gemfile.lock
index 8707a67ca4..26f619f637 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -178,7 +178,7 @@ GEM
       activesupport (>= 3.0.0)
       uniform_notifier (~> 1.11)
     byebug (11.1.3)
-    cable_ready (5.0.0.pre2)
+    cable_ready (5.0.0.pre3)
       rails (>= 5.2)
       thread-local (>= 1.1.0)
     cancancan (1.15.0)
@@ -703,7 +703,7 @@ DEPENDENCIES
   bugsnag
   bullet
   byebug
-  cable_ready (= 5.0.0.pre2)
+  cable_ready (= 5.0.0.pre3)
   cancancan (~> 1.15.0)
   capybara
   catalog!
diff --git a/app/controllers/concerns/order_stock_check.rb b/app/controllers/concerns/order_stock_check.rb
index 235056c0bb..a3c09d1838 100644
--- a/app/controllers/concerns/order_stock_check.rb
+++ b/app/controllers/concerns/order_stock_check.rb
@@ -25,7 +25,7 @@ module OrderStockCheck
   end
 
   def reset_order_to_cart
-    return if Flipper.enabled? :split_checkout
+    return if Flipper.enabled? :split_checkout, spree_current_user
 
     OrderCheckoutRestart.new(@order).call
   end
diff --git a/app/controllers/payment_gateways/stripe_controller.rb b/app/controllers/payment_gateways/stripe_controller.rb
index cb9331f3da..fc9cb1dd93 100644
--- a/app/controllers/payment_gateways/stripe_controller.rb
+++ b/app/controllers/payment_gateways/stripe_controller.rb
@@ -67,12 +67,16 @@ module PaymentGateways
       @valid_payment_intent ||= begin
         return false unless params["payment_intent"]&.starts_with?("pi_")
 
-        @order.state == "payment" &&
-          last_payment&.state == "requires_authorization" &&
-          last_payment&.response_code == params["payment_intent"]
+        order_and_payment_valid?
       end
     end
 
+    def order_and_payment_valid?
+      @order.state.in?(["payment", "confirmation"]) &&
+        last_payment&.state == "requires_authorization" &&
+        last_payment&.response_code == params["payment_intent"]
+    end
+
     def last_payment
       @last_payment ||= OrderPaymentFinder.new(@order).last_payment
     end
diff --git a/app/controllers/split_checkout_controller.rb b/app/controllers/split_checkout_controller.rb
index 19eb4da3a0..63ca43a42b 100644
--- a/app/controllers/split_checkout_controller.rb
+++ b/app/controllers/split_checkout_controller.rb
@@ -22,6 +22,8 @@ class SplitCheckoutController < ::BaseController
 
   def update
     if confirm_order || update_order
+      return if performed?
+
       clear_invalid_payments
       advance_order_state
       redirect_to_step
@@ -45,12 +47,27 @@ class SplitCheckoutController < ::BaseController
     return unless validate_summary! && @order.errors.empty?
 
     @order.customer.touch :terms_and_conditions_accepted_at
+
+    return true if redirect_to_payment_gateway
+
     @order.confirm!
     order_completion_reset @order
   end
 
+  def redirect_to_payment_gateway
+    return unless selected_payment_method&.external_gateway?
+    return unless (redirect_url = selected_payment_method.external_payment_url(order: @order))
+
+    render operations: cable_car.redirect_to(url: URI(redirect_url))
+    true
+  end
+
+  def selected_payment_method
+    @selected_payment_method ||= Checkout::PaymentMethodFetcher.new(@order).call
+  end
+
   def update_order
-    return if @order.errors.any?
+    return if params[:confirm_order] || @order.errors.any?
 
     @order.select_shipping_method(params[:shipping_method_id])
     @order.update(order_params)
@@ -95,7 +112,7 @@ class SplitCheckoutController < ::BaseController
   end
 
   def order_params
-    @order_params ||= Checkout::Params.new(@order, params).call
+    @order_params ||= Checkout::Params.new(@order, params, spree_current_user).call
   end
 
   def redirect_to_step
diff --git a/app/models/spree/order.rb b/app/models/spree/order.rb
index aa08cca513..c050fc93ca 100644
--- a/app/models/spree/order.rb
+++ b/app/models/spree/order.rb
@@ -24,8 +24,8 @@ module Spree
         order.update_totals
         order.payment_required?
       }
-      go_to_state :confirmation, if: ->(_order) {
-        Flipper.enabled? :split_checkout
+      go_to_state :confirmation, if: ->(order) {
+        Flipper.enabled? :split_checkout, order.created_by
       }
       go_to_state :complete
     end
diff --git a/app/services/checkout/params.rb b/app/services/checkout/params.rb
index 10715c8acc..cef90428e8 100644
--- a/app/services/checkout/params.rb
+++ b/app/services/checkout/params.rb
@@ -2,9 +2,10 @@
 
 module Checkout
   class Params
-    def initialize(order, params)
+    def initialize(order, params, current_user)
       @params = params
       @order = order
+      @current_user = current_user
     end
 
     def call
@@ -13,17 +14,18 @@ module Checkout
       apply_strong_parameters
       set_address_details
       set_payment_amount
+      set_existing_card
 
       @order_params
     end
 
     private
 
-    attr_reader :params, :order
+    attr_reader :params, :order, :current_user
 
     def apply_strong_parameters
       @order_params = params.require(:order).permit(
-        :email, :shipping_method_id, :special_instructions, :existing_card_id,
+        :email, :shipping_method_id, :special_instructions,
         :save_bill_address, :save_ship_address,
         bill_address_attributes: ::PermittedAttributes::Address.attributes,
         ship_address_attributes: ::PermittedAttributes::Address.attributes,
@@ -50,6 +52,22 @@ module Checkout
       @order_params[:payments_attributes].first[:amount] = order.total
     end
 
+    def set_existing_card
+      return unless existing_card_selected?
+
+      card = Spree::CreditCard.find(params[:existing_card_id])
+
+      if card.user_id.blank? || card.user_id != current_user&.id
+        raise Spree::Core::GatewayError, I18n.t(:invalid_credit_card)
+      end
+
+      @order_params[:payments_attributes].first[:source] = card
+    end
+
+    def existing_card_selected?
+      @order_params[:payments_attributes] && params[:existing_card_id].present?
+    end
+
     def addresses_present?
       @order_params[:ship_address_attributes] && @order_params[:bill_address_attributes]
     end
diff --git a/app/services/checkout/payment_method_fetcher.rb b/app/services/checkout/payment_method_fetcher.rb
new file mode 100644
index 0000000000..15b1829325
--- /dev/null
+++ b/app/services/checkout/payment_method_fetcher.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module Checkout
+  class PaymentMethodFetcher
+    def initialize(order)
+      @order = order
+    end
+
+    def call
+      latest_payment&.payment_method
+    end
+
+    private
+
+    attr_reader :order
+
+    def latest_payment
+      order.payments.order(:created_at).last
+    end
+  end
+end
diff --git a/app/views/split_checkout/payment/_stripe_sca.html.haml b/app/views/split_checkout/payment/_stripe_sca.html.haml
index f75a3b2aa8..36b9cb5adb 100644
--- a/app/views/split_checkout/payment/_stripe_sca.html.haml
+++ b/app/views/split_checkout/payment/_stripe_sca.html.haml
@@ -3,7 +3,7 @@
     .checkout-input
       %label
         = t('split_checkout.step2.form.stripe.use_saved_card')
-      = select_tag :existing_card,
+      = select_tag :existing_card_id,
         options_for_select(stripe_card_options(@saved_credit_cards) + [[t('split_checkout.step2.form.stripe.create_new_card'), ""]], @selected_card),
         { "data-action": "change->stripe-cards#onSelectCard", "data-stripe-cards-target": "select" }
 
diff --git a/package.json b/package.json
index b465a2acc6..a0fcde890d 100644
--- a/package.json
+++ b/package.json
@@ -29,7 +29,7 @@
     "@hotwired/turbo": "^7.1.0",
     "@rails/webpacker": "5.4.3",
     "babel-loader": "^8.2.3",
-    "cable_ready": "^5.0.0-pre2",
+    "cable_ready": "5.0.0-pre3",
     "flatpickr": "^4.6.9",
     "foundation-sites": "^5.5.2",
     "jquery-ui": "1.13.0",
diff --git a/spec/controllers/payment_gateways/stripe_controller_spec.rb b/spec/controllers/payment_gateways/stripe_controller_spec.rb
index 596702fac4..d1819cccfb 100644
--- a/spec/controllers/payment_gateways/stripe_controller_spec.rb
+++ b/spec/controllers/payment_gateways/stripe_controller_spec.rb
@@ -46,17 +46,21 @@ module PaymentGateways
           order.payments << payment
         end
 
-        it "completes the order and redirects to the order confirmation page" do
-          expect(controller).to receive(:processing_succeeded).and_call_original
-          expect(controller).to receive(:order_completion_reset).and_call_original
+        shared_examples "successful order completion" do
+          it "completes the order and redirects to the order confirmation page" do
+            expect(controller).to receive(:processing_succeeded).and_call_original
+            expect(controller).to receive(:order_completion_reset).and_call_original
 
-          get :confirm, params: { payment_intent: "pi_123" }
+            get :confirm, params: { payment_intent: "pi_123" }
 
-          expect(order.completed?).to be true
-          expect(response).to redirect_to order_path(order, order_token: order.token)
-          expect(flash[:notice]).to eq I18n.t(:order_processed_successfully)
+            expect(order.completed?).to be true
+            expect(response).to redirect_to order_path(order, order_token: order.token)
+            expect(flash[:notice]).to eq I18n.t(:order_processed_successfully)
+          end
         end
 
+        include_examples "successful order completion"
+
         it "creates a customer record" do
           order.update_columns(customer_id: nil)
           Customer.delete_all
@@ -65,6 +69,17 @@ module PaymentGateways
             get :confirm, params: { payment_intent: "pi_123" }
           }.to change { Customer.count }.by(1)
         end
+
+        context "using split checkout" do
+          before do
+            allow(Flipper).to receive(:enabled?).with(:split_checkout) { true }
+            allow(Flipper).to receive(:enabled?).with(:split_checkout, anything) { true }
+
+            order.update_attribute :state, "confirmation"
+          end
+
+          include_examples "successful order completion"
+        end
       end
 
       context "when the order is not in payment state" do
diff --git a/spec/controllers/split_checkout_controller_spec.rb b/spec/controllers/split_checkout_controller_spec.rb
index 9c8963a349..9d73967e63 100644
--- a/spec/controllers/split_checkout_controller_spec.rb
+++ b/spec/controllers/split_checkout_controller_spec.rb
@@ -141,6 +141,28 @@ describe SplitCheckoutController, type: :controller do
           expect(order.reload.state).to eq "confirmation"
         end
       end
+
+      context "with a saved credit card" do
+        let!(:saved_card) { create(:stored_credit_card, user: user) }
+        let(:checkout_params) do
+          {
+            order: {
+              payments_attributes: [
+                { payment_method_id: payment_method.id }
+              ]
+            },
+            existing_card_id: saved_card.id
+          }
+        end
+
+        it "updates and redirects to payment step" do
+          put :update, params: params
+
+          expect(response).to redirect_to checkout_step_path(:summary)
+          expect(order.reload.state).to eq "confirmation"
+          expect(order.payments.first.source.id).to eq saved_card.id
+        end
+      end
     end
 
     context "summary step" do
@@ -193,6 +215,24 @@ describe SplitCheckoutController, type: :controller do
           end
         end
       end
+
+      context "when an external payment gateway is used" do
+        before do
+          expect(Checkout::PaymentMethodFetcher).
+            to receive_message_chain(:new, :call) { payment_method }
+          expect(payment_method).to receive(:external_gateway?) { true }
+          expect(payment_method).to receive(:external_payment_url) { "https://example.com/pay" }
+        end
+
+        describe "confirming the order" do
+          it "redirects to the payment gateway's URL" do
+            put :update, params: params
+
+            expect(response.body).to match("https://example.com/pay").and match("redirect")
+            expect(order.reload.state).to eq "confirmation"
+          end
+        end
+      end
     end
   end
 end
diff --git a/spec/services/checkout/payment_method_fetcher_spec.rb b/spec/services/checkout/payment_method_fetcher_spec.rb
new file mode 100644
index 0000000000..3607eac7fc
--- /dev/null
+++ b/spec/services/checkout/payment_method_fetcher_spec.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Checkout::PaymentMethodFetcher do
+  let!(:order) { create(:completed_order_with_totals) }
+  let(:payment1) { build(:payment, order: order) }
+  let(:payment2) { build(:payment, order: order) }
+  let(:service) { Checkout::PaymentMethodFetcher.new(order) }
+
+  describe '#call' do
+    context "when the order has payments" do
+      before do
+        order.payments << payment1
+        order.payments << payment2
+      end
+
+      it "returns the payment_method of the most recently created payment" do
+        expect(service.call).to eq payment2.payment_method
+      end
+    end
+
+    context "when the order has no payments" do
+      it "returns nil" do
+        expect(service.call).to be_nil
+      end
+    end
+  end
+end
diff --git a/yarn.lock b/yarn.lock
index 9d9d1b1f78..60d19df993 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -4134,10 +4134,10 @@ bytes@3.1.0:
   resolved "https://registry.yarnpkg.com/bytes/-/bytes-3.1.0.tgz#f6cf7933a360e0588fa9fde85651cdc7f805d1f6"
   integrity sha512-zauLjrfCG+xvoyaqLoV8bLVXXNGC4JqlxFCutSDWA6fJrTo2ZuvLYTqZ7aHBLZSMOopbzwv8f+wZcVzfVTI2Dg==
 
-cable_ready@^5.0.0-pre2:
-  version "5.0.0-pre2"
-  resolved "https://registry.yarnpkg.com/cable_ready/-/cable_ready-5.0.0-pre2.tgz#c3589ebfe28a10db3998ae3711d31a072be53bfb"
-  integrity sha512-/Ql2e/Hz0kRRKzzz06sMXFm3+/qacYqSHfWkdt1CcsI7I6OOOhHzPAgY8VS+zqa/6+ggjWoPqHyi8Hr6j/0O6w==
+cable_ready@5.0.0-pre3:
+  version "5.0.0-pre3"
+  resolved "https://registry.yarnpkg.com/cable_ready/-/cable_ready-5.0.0-pre3.tgz#d36bb9648aead748dfdf0f46dfb489799733f330"
+  integrity sha512-jFjTJ/K/AiVIgjKr63qXGzp9xZOt2/2UyjVpkMkSzFyDHlYILOwnK4WofGwBKS6tXwDZMfohbIzW/p+LKbrlgA==
   dependencies:
     morphdom "^2.6.1"