Total cost including taxes/fees disclosed before payment

When checkout shows a base price and applies taxes silently on charge, the first time a user sees the true total is on their bank statement — a direct violation of FTC Negative Option Rule (2025) transparency requirements and EU Consumer Rights Directive 2011/83/EU Article 6 pre-contract information obligations. Jurisdictions with sales tax on SaaS (Texas, Ohio, Washington, and most EU member states) make this gap material and frequent. Silent tax additions are also the second most-cited cause of subscription chargebacks after unrecognized recurring charges.

Show a tax-inclusive price summary before the payment submit button. For Stripe Checkout, enable automatic_tax and Stripe will display the breakdown:

const session = await stripe.checkout.sessions.create({
  mode: 'subscription',
  automatic_tax: { enabled: true },
})

For custom checkout forms, call a preview endpoint and render an order summary in app/(checkout)/checkout/page.tsx:

<div className="order-summary">
  <div className="line-item"><span>Pro Plan (monthly)</span><span>$29.00</span></div>
  <div className="line-item"><span>Tax</span><span>{tax > 0 ? formatCents(tax) : 'Calculated at checkout'}</span></div>
  <div className="line-item total"><strong>Total due today</strong><strong>{formatCents(total)}</strong></div>
</div>

The total must appear before, not after, the submit button.