Common Product Requirements

# Payment Checkout Flow Requirements

**Proposed file:** `docs/prd/prd-payment-checkout.md`  
**Slug:** `payment-checkout`  
**feature_status:** Draft — discovery assumptions require Product approval.

## Discovery assumptions

- **What outcome:** Increase completed purchases by giving authenticated shoppers a clear, trustworthy payment experience.
- **Which channels:** Responsive web and mobile web; native mobile is TBD.
- **Persona:** Authenticated shopper with items in a valid cart.
- **Business objective:**  
  - `OBJ-1`: Increase successful checkout completion.  
  - `OBJ-2`: Reduce payment-related support contacts and duplicate charges.  
  - `OBJ-3`: Maintain secure, auditable payment processing.
- **Payment methods:** Credit/debit cards and provider-supported wallets. Exact provider and regional methods are TBD.
- **Currency, tax, shipping, refunds, and saved-payment rules:** TBD.

## Scope

The flow must allow a shopper to:

1. Review cart, shipping, taxes, discounts, and final total.
2. Enter or select a billing and payment method.
3. Validate required fields before submission.
4. Submit payment securely.
5. See success, failure, cancellation, and retry states.
6. Receive an order confirmation with an order reference.
7. Prevent duplicate submissions and duplicate order creation.

## Requirements

| ID | Requirement | Owner | Status | Priority | Verification lane | Objective |
|---|---|---|---|---|---|---|
| `REQ-PC-001` | Display an accurate order summary, including items, quantities, subtotal, shipping, tax, discounts, currency, and payable total. | Product Manager | Proposed | P0 | UI and API test | `OBJ-1` |
| `REQ-PC-002` | Allow the shopper to enter billing details and choose an available payment method. | Engineering Lead | Proposed | P0 | Functional and integration test | `OBJ-1` |
| `REQ-PC-003` | Validate required fields and payment-method constraints before payment submission, with actionable field-level errors. | Engineering Lead | Proposed | P0 | Negative-path QA | `OBJ-1` |
| `REQ-PC-004` | Submit payment through the approved payment provider without exposing raw payment credentials to application logs or storage. | Engineering Lead | Proposed | P0 | Security and provider integration test | `OBJ-3` |
| `REQ-PC-005` | Disable repeated submission while authorization is pending and make payment submission idempotent. | Engineering Lead | Proposed | P0 | Concurrency and integration test | `OBJ-2` |
| `REQ-PC-006` | Present distinct states for success, declined payment, provider error, cancellation, timeout, and recoverable network failure. | Product Manager | Proposed | P0 | State-transition QA | `OBJ-1`, `OBJ-2` |
| `REQ-PC-007` | On confirmed success, create or confirm exactly one order and show the order reference and next steps. | Engineering Lead | Proposed | P0 | End-to-end test | `OBJ-1`, `OBJ-2` |
| `REQ-PC-008` | Provide a safe retry path that preserves the cart and does not create another charge or order. | Engineering Lead | Proposed | P0 | Recovery-path QA | `OBJ-2` |
| `REQ-PC-009` | Record checkout and payment outcomes for analytics, reconciliation, and support investigation without storing sensitive payment data. | Product Manager / Support Ops | Proposed | P1 | Analytics and audit verification | `OBJ-2`, `OBJ-3` |
| `REQ-PC-010` | Provide accessible, responsive checkout behavior on supported web and mobile-web breakpoints. | QA/Release Lead | Proposed | P1 | Accessibility and responsive UI test | `OBJ-1` |

## Acceptance criteria

### `REQ-PC-001` — Order summary

- `AC-PC-001` — Given a valid cart, when the shopper opens checkout, then the page displays the current items, quantities, subtotal, shipping, tax, discounts, currency, and final payable total.
- `AC-PC-002` — Given the cart or pricing changes before payment, when the shopper attempts to pay, then the system recalculates the total and requires confirmation before authorization.
- `AC-PC-003` — Given an empty or expired cart, when the shopper opens checkout, then the system shows a zero/error state and prevents payment submission.

### `REQ-PC-002` — Payment entry

- `AC-PC-004` — Given an available payment method, when the shopper selects it, then the corresponding required fields or provider-controlled payment UI are displayed.
- `AC-PC-005` — Given unsupported regional, currency, or payment-method conditions, when checkout loads, then unavailable methods are hidden or clearly marked unavailable.

### `REQ-PC-003` — Validation

- `AC-PC-006` — Given missing or invalid required data, when the shopper submits checkout, then payment is not attempted and each invalid field displays an actionable error.
- `AC-PC-007` — Given valid checkout data, when the shopper submits, then client-side validation passes and payment processing begins.

### `REQ-PC-004` — Secure authorization

- `AC-PC-008` — Given valid payment details, when authorization starts, then the application uses the approved provider integration and does not log or persist raw card data, CVV, or equivalent secrets.
- `AC-PC-009` — Given provider-required authentication such as 3-D Secure, when the provider requests it, then the shopper can complete the challenge and return to checkout.

### `REQ-PC-005` — Duplicate prevention

- `AC-PC-010` — Given a payment request is pending, when the shopper selects Pay again, then no second request is submitted.
- `AC-PC-011` — Given the same idempotency key is submitted more than once, when the provider or checkout service receives it, then only one charge and one order result are produced.

### `REQ-PC-006` — Outcome states

- `AC-PC-012` — Given successful authorization, when order confirmation completes, then the shopper sees a success state with the order reference.
- `AC-PC-013` — Given a declined payment, when the provider returns a decline, then the shopper sees a clear explanation, retains the cart, and can choose another method or retry.
- `AC-PC-014` — Given cancellation, timeout, or recoverable network failure, when payment status is unresolved, then the shopper is told not to resubmit blindly and is given a status-check or support path.
- `AC-PC-015` — Given an unrecoverable provider error, when checkout fails, then no success confirmation is shown and the shopper can safely retry.

### `REQ-PC-007` and `REQ-PC-008` — Order confirmation and recovery

- `AC-PC-016` — Given a confirmed successful payment, when the shopper refreshes or revisits the result, then the same order reference is shown and no additional order is created.
- `AC-PC-017` — Given payment authorization succeeded but the confirmation response was interrupted, when the shopper returns to checkout, then the system checks payment/order status before offering retry.
- `AC-PC-018` — Given a failed payment, when the shopper retries, then the cart remains intact and the previous failed attempt is not charged again.

### `REQ-PC-009` and `REQ-PC-010` — Analytics and quality

- `AC-PC-019` — Given checkout activity, when the relevant state occurs, then analytics record checkout viewed, payment method selected, payment submitted, payment succeeded, payment failed, and checkout abandoned.
- `AC-PC-020` — Given analytics or logging, when payment data is processed, then sensitive payment credentials are excluded.
- `AC-PC-021` — Given keyboard, screen-reader, or mobile viewport usage, when the shopper completes checkout, then controls, errors, focus order, and status messages remain usable.

## Non-functional requirements

- Checkout summary rendering target: under 200 ms p95 after required data is available.
- Payment authorization timeout and provider retry policy: TBD with Engineering and payment-provider constraints.
- Payment operations must use encrypted transport and provider-compliant tokenization.
- Secrets and payment credentials must not appear in logs, analytics payloads, URLs, or client persistence.
- Offline mode: payment authorization is unsupported. If connectivity is lost, preserve the cart where safe and show an unresolved-payment recovery state.
- Availability, accessibility conformance level, supported browsers, and regional compliance requirements: TBD.

## Analytics and operations

Track:

- `checkout_viewed`
- `payment_method_selected`
- `payment_submitted`
- `payment_succeeded`
- `payment_failed`
- `checkout_abandoned`
- `payment_status_recovered`

Guardrails:

- Duplicate-charge rate.
- Duplicate-order rate.
- Payment failure rate by method and provider response.
- Checkout completion rate.
- Unresolved-payment count.
- Payment-related support contacts.

Support Ops must have access to a non-sensitive order/payment reference and provider status sufficient to investigate failures.

## Technical constraints and decisions

- Payment provider, API contract, webhook requirements, idempotency-key format, and supported payment methods are TBD.
- Database impacts are TBD; likely entities include order payment status, provider transaction reference, authorization state, and reconciliation metadata.
- No raw payment credentials may be stored.
- `design-solution` is required before implementation because provider integration, API contracts, persistence, and failure recovery remain unresolved.
- Existing code without this PRD and AC evidence is partial/unverified and must pass `implementation-readiness`.

## RACI and handoff gate

- **Product Manager:** Accountable for scope, business objectives, and acceptance criteria.
- **Engineering Lead:** Responsible for provider integration, API behavior, idempotency, persistence, and security controls.
- **QA/Release Lead:** Responsible for functional, negative-path, accessibility, and release verification.
- **Support Ops:** Consulted on diagnostics, customer messaging, and support readiness.
- **Security/Compliance:** Consulted on payment-data handling and regulatory constraints.

Engineering handoff is blocked until each implementation slice names its `REQ-*`, `AC-*`, owner, status, priority, and verification lane.

## Out of scope

- Refunds, disputes, chargebacks, and subscription billing.
- Payment-provider selection and contract negotiation.
- Tax or shipping-rate calculation logic.
- Loyalty points, gift cards, buy-now-pay-later, and native mobile checkout unless separately approved.
- Saved cards unless explicitly included in the approved payment-provider design.

## Open decisions

1. Which payment provider and payment methods are supported?
2. Which channels and countries/currencies are in the first release?
3. Are guest checkout and saved payment methods required?
4. What are the timeout, reconciliation, and customer-notification policies?
5. What measurable targets define success for `OBJ-1` through `OBJ-3`?

**Recommended next workflow:** resolve discovery questions, then run `design-solution`, followed by `implementation-readiness`.