Written confirmation sent after enrollment with all terms

FTC Negative Option Rule (2025) and California ARL both require written confirmation of subscription enrollment including material terms — price, billing period, next billing date, and cancellation instructions. Stripe's default payment receipt satisfies the payment acknowledgment but does not include a cancellation path, which is the regulatory requirement most commonly cited in enforcement guidance. The confirmation email also serves as the user's primary reference if they want to cancel before the next billing date; without it, support tickets and chargebacks increase measurably.

Handle the checkout.session.completed Stripe webhook and send a custom confirmation email that includes all material terms. In app/api/webhooks/stripe/route.ts:

if (event.type === 'checkout.session.completed') {
  const subscription = await stripe.subscriptions.retrieve(
    session.subscription as string
  )
  await sendEmail({
    to: session.customer_email!,
    subject: 'Your subscription is confirmed',
    template: 'subscription-confirmation',
    data: {
      planName: subscription.items.data[0]?.plan.nickname ?? 'Pro Plan',
      price: (subscription.items.data[0]?.plan.amount ?? 0) / 100,
      period: subscription.items.data[0]?.plan.interval ?? 'month',
      nextBillingDate: formatDate(subscription.current_period_end),
      cancelUrl: `${process.env.NEXT_PUBLIC_APP_URL}/settings/billing`,
    },
  })
}

The email template must include plan name, amount, billing frequency, next charge date, and a sentence: 'To cancel, visit [link] before [next billing date].'