Grab and show the next amount to pay from Stripe

saas/app/controllers/stripe/webhooks_controller.rb

@@ -48,7 +48,8 @@ class Stripe::WebhooksController < ApplicationController
           stripe_subscription_id: stripe_subscription.id,
           status: stripe_subscription.status,
           current_period_end: current_period_end_for(stripe_subscription),
-          cancel_at: stripe_subscription.cancel_at ? Time.at(stripe_subscription.cancel_at) : nil
+          cancel_at: stripe_subscription.cancel_at ? Time.at(stripe_subscription.cancel_at) : nil,
+          next_amount_due_in_cents: next_amount_due_for(stripe_subscription)
         }
 
         yield subscription_properties if block_given?
@@ -66,4 +67,13 @@ class Stripe::WebhooksController < ApplicationController
       timestamp = stripe_subscription.items.data.first&.current_period_end
       Time.at(timestamp) if timestamp
     end
+
+    def next_amount_due_for(stripe_subscription)
+      return nil if stripe_subscription.status == "canceled"
+
+      preview = Stripe::Invoice.create_preview(customer: stripe_subscription.customer, subscription: stripe_subscription.id)
+      preview.amount_due
+    rescue Stripe::InvalidRequestError
+      nil
+    end
 end

saas/app/helpers/subscriptions_helper.rb

@@ -5,7 +5,7 @@ module SubscriptionsHelper
     elsif subscription.canceled?
       "Your Fizzy subscription ended on"
     else
-      "Your next payment of <b>$#{ subscription.plan.price }</b> will be billed on".html_safe
+      "Your next payment of <b>#{ number_to_currency(subscription.next_amount_due) }</b> will be billed on".html_safe
     end
   end
 end

saas/app/models/account/subscription.rb

@@ -14,4 +14,8 @@ class Account::Subscription < SaasRecord
   def to_be_canceled?
     active? && cancel_at.present?
   end
+
+  def next_amount_due
+    next_amount_due_in_cents ? next_amount_due_in_cents / 100.0 : plan.price
+  end
 end

saas/db/migrate/20251215170000_add_next_amount_due_in_cents_to_account_subscriptions.rb

@@ -0,0 +1,5 @@
+class AddNextAmountDueInCentsToAccountSubscriptions < ActiveRecord::Migration[8.2]
+  def change
+    add_column :account_subscriptions, :next_amount_due_in_cents, :integer
+  end
+end

saas/db/saas_schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.2].define(version: 2025_12_15_160000) do
+ActiveRecord::Schema[8.2].define(version: 2025_12_15_170000) do
   create_table "account_billing_waivers", id: :uuid, charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.uuid "account_id", null: false
     t.datetime "created_at", null: false
@@ -31,6 +31,7 @@ ActiveRecord::Schema[8.2].define(version: 2025_12_15_160000) do
     t.datetime "cancel_at"
     t.datetime "created_at", null: false
     t.datetime "current_period_end"
+    t.integer "next_amount_due_in_cents"
     t.string "plan_key"
     t.string "status"
     t.string "stripe_customer_id", null: false

saas/test/controllers/stripe/webhooks_controller_test.rb

@@ -29,6 +29,7 @@ class Stripe::WebhooksControllerTest < ActionDispatch::IntegrationTest
 
     Stripe::Webhook.stubs(:construct_event).returns(event)
     Stripe::Subscription.stubs(:retrieve).returns(stripe_sub)
+    Stripe::Invoice.stubs(:create_preview).returns(OpenStruct.new(amount_due: 1999))
 
     post stripe_webhooks_path
 
@@ -38,7 +39,7 @@ class Stripe::WebhooksControllerTest < ActionDispatch::IntegrationTest
     assert_equal "active", @subscription.status
   end
 
-  test "subscription updated changes status" do
+  test "subscription updated changes status and syncs next amount due" do
     @subscription.update!(stripe_subscription_id: "sub_123", status: "active")
 
     stripe_sub = OpenStruct.new(
@@ -53,11 +54,14 @@ class Stripe::WebhooksControllerTest < ActionDispatch::IntegrationTest
 
     Stripe::Webhook.stubs(:construct_event).returns(event)
     Stripe::Subscription.stubs(:retrieve).returns(stripe_sub)
+    Stripe::Invoice.stubs(:create_preview).returns(OpenStruct.new(amount_due: 1999))
 
     post stripe_webhooks_path
 
     assert_response :ok
-    assert_equal "past_due", @subscription.reload.status
+    @subscription.reload
+    assert_equal "past_due", @subscription.status
+    assert_equal 1999, @subscription.next_amount_due_in_cents
   end
 
   test "subscription deleted cancels subscription" do
@@ -82,6 +86,7 @@ class Stripe::WebhooksControllerTest < ActionDispatch::IntegrationTest
     @subscription.reload
     assert_equal "canceled", @subscription.status
     assert_nil @subscription.stripe_subscription_id
+    assert_nil @subscription.next_amount_due_in_cents
   end
 
   private