AshBilling

Welcome! ash_billing provides declarative billing, subscriptions, and payment providers for the Ash Framework. This documentation is best viewed on hexdocs.

Inspired by Laravel Cashier and Rails Pay, ash_billing offers a unified, declarative architecture to handle customers, checkout sessions, customer billing portals, and recurring subscription lifecycles natively in Ash.

About the Documentation

Tutorials walk you through a series of steps to accomplish a goal. These are learning-oriented, and are a great place for beginners to start.

Topics provide a high-level overview of a specific concept or feature. These are understanding-oriented, and are perfect for discovering design patterns, features, and operational architecture.

Reference documentation is produced automatically from our source code. It comes in the form of module documentation and DSL documentation. This documentation is information-oriented. Use the sidebar and the search bar to find relevant reference information.

Tutorials

• Getting Started with AshBilling

Topics

• Webhooks & Operational Resilience

Reference

• AshBilling.Resource DSL
• AshBilling.Subscription DSL
• AshBilling.WebhookEvent DSL
• For other reference documentation, see the sidebar & search bar

Related Packages

• Ash Framework

• Igniter | Project setup and automated code generation

• AshPostgres | PostgreSQL data layer for Ash

• AshAuthentication | Authentication extension for Ash

Features

• Declarative Spark DSL: Add billing customer or subscription capabilities to any Ash resource with clean DSL blocks (billing do ... end and billing_subscription do ... end).
• Compile-Time Spark Verifiers: Automatic validation of relationship existence and attribute type safety during compilation.
• Stripe Provider: First-class support for Stripe Checkout Sessions, Customer Billing Portal, and Recurring Subscriptions.
• Secure Webhook Plug: Phoenix/Plug endpoint with constant-time HMAC-SHA256 signature verification and replay attack protection.
• Automatic Retries via HTTP 500 Protocol: Responds with HTTP 500 when database synchronization fails, triggering Stripe's automated exponential retry backoff.
• Modular Provider Architecture: Built with an extensible AshBilling.Provider behaviour, ready for Stripe, Paddle, LemonSqueezy, and more.
• 100% Testable: Zero external HTTP calls needed during test suites thanks to plug-based stubs and polymorphic extractors.

Installation

The recommended way to install ash_billing is using Igniter:

mix igniter.install ash_billing

Igniter automatically adds the dependency to mix.exs, configures your customer and subscription resources, mounts the webhook route in your Phoenix router, and sets up runtime configuration.

Alternatively, you can install it manually by adding ash_billing to your mix.exs:

def deps do
  [
    {:ash_billing, "~> 0.1.1"}
  ]
end

Quickstart

1. Add Billing to your User Resource

defmodule MyApp.Accounts.User do
  use Ash.Resource,
    domain: MyApp.Accounts,
    extensions: [AshBilling.Resource]

  attributes do
    uuid_primary_key :id
    attribute :email, :string, public?: true
    attribute :name, :string, public?: true
  end

  billing do
    # Defaults to :stripe_customer_id
    customer_id_attribute :stripe_customer_id
    provider AshBilling.Providers.Stripe
  end
end

2. Define a Subscription Resource

defmodule MyApp.Billing.Subscription do
  use Ash.Resource,
    domain: MyApp.Billing,
    extensions: [AshBilling.Subscription]

  attributes do
    uuid_primary_key :id
  end

  relationships do
    belongs_to :user, MyApp.Accounts.User
  end

  billing_subscription do
    customer_relationship :user
    provider AshBilling.Providers.Stripe
  end
end

The extension automatically manages attributes such as :provider_subscription_id, :status, :price_id, :current_period_end, and :cancel_at_period_end, and generates :active? and :on_trial? calculations.

3. Mount the Webhook Handler in your Phoenix Router

# lib/my_app_web/router.ex
scope "/webhooks" do
  forward "/stripe", AshBilling.Plug,
    provider: AshBilling.Providers.Stripe,
    webhook_secret: {System, :get_env, ["STRIPE_WEBHOOK_SECRET"]},
    customer_resource: MyApp.Accounts.User,
    subscription_resource: MyApp.Billing.Subscription,
    domain: MyApp.Billing
end

AshBilling.Plug verifies the HMAC signature and automatically synchronizes customer and subscription states. You can also pass an optional handler: MyApp.Billing.WebhookHandler if you want to listen to custom Stripe events.

[!NOTE] In Phoenix applications, ensure AshBilling.Plug has access to the raw request body for cryptographic signature verification. You can mount it in endpoint.ex before Plug.Parsers, or configure a body_reader in Plug.Parsers that populates conn.assigns[:raw_body].

High-Level API

Create a Customer

{:ok, customer_id} = AshBilling.create_customer(user)

Start a Checkout Session

{:ok, session} = AshBilling.create_checkout_session(user,
  price: "price_pro_monthly",
  success_url: "https://myapp.com/billing?success=true",
  cancel_url: "https://myapp.com/billing?canceled=true"
)

# Redirect the user to session.url

Open the Customer Billing Portal

{:ok, portal} = AshBilling.create_portal_session(user,
  return_url: "https://myapp.com/dashboard"
)

# Redirect the user to portal.url

Check Subscription Status

# Check if user has any active/trialing subscription
AshBilling.subscribed?(user)

# Check if user has a specific plan
AshBilling.subscribed?(user, "price_pro_monthly")

Swap Subscription Plans (Upgrades / Downgrades)

# Upgrade to an annual or higher-tier plan with automatic proration
{:ok, updated_sub} = AshBilling.swap_plan(user_subscription, "price_enterprise_annual",
  proration_behavior: "create_prorations"
)

# Update seat quantities (per-seat billing)
{:ok, updated_sub} = AshBilling.update_quantity(user_subscription, 10)

Resume a Canceled Subscription

# Reactivate a subscription that was scheduled to cancel at period end
{:ok, resumed_sub} = AshBilling.resume_subscription(user_subscription)

Declarative Ash Policies

Protect any resource action declaratively based on billing status using native Ash policy checks:

defmodule MyApp.AI.Prompt do
  use Ash.Resource,
    domain: MyApp.AI,
    authorizers: [Ash.Policy.Authorizer]

  policies do
    # Authorize any user with an active subscription or ongoing trial
    policy action(:generate) do
      authorize_if AshBilling.Checks.Subscribed
    end

    # Require a specific plan tier (e.g., Enterprise)
    policy action(:export_fine_tuned_weights) do
      authorize_if {AshBilling.Checks.HasPrice, price: "price_enterprise_annual"}
    end
  end
end

Webhook Deduplication (Single-Node & Clustered)

ash_billing provides two deduplication strategies to prevent double-processing on Stripe webhook retries:

1. In-Memory ETS (:memory, default)

Zero-configuration in-memory ETS table with automatic 24-hour TTL cleanup. Ideal for single-server deployments and local development.

2. Database-Backed Resource (:resource)

Guarantees deduplication across multi-node clusters (e.g., Fly.io, Kubernetes, AWS ECS) using an Ash resource backed by your database (PostgreSQL, SQLite, MySQL).

Define a webhook event resource:

defmodule MyApp.Billing.WebhookEvent do
  use Ash.Resource,
    domain: MyApp.Billing,
    extensions: [AshBilling.WebhookEvent]

  actions do
    default_accept :*
    defaults [:read, :create]
  end
end

Then configure it in your router:

forward "/webhooks/stripe", AshBilling.Plug,
  customer_resource: MyApp.Accounts.User,
  subscription_resource: MyApp.Billing.Subscription,
  deduplication_resource: MyApp.Billing.WebhookEvent

Configuration

Configure your Stripe API credentials in config/runtime.exs:

config :ash_billing,
  stripe_api_key: System.get_env("STRIPE_SECRET_KEY"),
  stripe_webhook_secret: System.get_env("STRIPE_WEBHOOK_SECRET")

Telemetry

ash_billing emits standard :telemetry spans across all critical operations, enabling real-time monitoring via Grafana, AppSignal, Datadog, or Prometheus:

Supported Stripe API Baseline

ash_billing targets modern Stripe API versions (2023-10-16 through current releases). Payloads are parsed defensively with polymorphic fallback resolvers for customer objects, plans, prices, and timestamps, ensuring backward and forward compatibility across API upgrades.

Security, Financial Responsibility & Support Scope

• Financial Compliance: Tax calculation, invoice finalization, currency conversion rules, and PCI-DSS compliance boundaries remain the architectural responsibility of the implementing application.
• Webhook Resilience: In production environments, always pair AshBilling.Plug with a database-backed deduplication resource (AshBilling.WebhookEvent) to ensure idempotency across multi-node deployments and automatic Stripe exponential retries.
• Support & Issues: The issue tracker is strictly reserved for reproducible bugs and targeted feature enhancements. For architecture questions and implementation advice, please participate in the Ash Discord or Elixir Forum.

Community & Support

• Ask questions on the Ash Discord
• Discuss on the Elixir Forum
• Official Ash Framework Website: ash-hq.org

License

MIT License. Copyright (c) 2026 Alejandro Felix.