PaymentIQ API & cashier integration checklist.

1. Define the payment journey

Write down the methods, currencies, markets and transaction types you intend to launch. Identify who owns the merchant application, cashier, PaymentIQ configuration and provider account. A simple ownership list makes an ambiguous failure easier to route to the right team.

• Choose test or production explicitly and confirm the required permissions.
• Identify the cashier or Hosted Fields approach and the supported versions in the current vendor documentation.
• Agree the expected deposit, withdrawal and cancellation journeys that apply to the project.

2. Follow identity and session handling

Use the official documentation for the exact API contracts. Trace how your application creates and passes the required user and session context, and how expired or invalid sessions are handled. Test this from the actual merchant application rather than relying only on a standalone demo.

• Verify the merchant and environment configuration used by each component.
• Check the behaviour of an expired session, a repeated user action and an interrupted redirect.
• Document which system is responsible for displaying the final result to the user.

When a test does not reach the expected result, use the failed-payment troubleshooting guide.

3. Check methods, providers and routing

Confirm that the intended methods are available for the test customer and that the provider configuration matches the agreed setup. Review routing conditions and any fallback logic against the flows you actually want to run.

• Check method availability for the selected market, currency and customer scenario.
• Confirm provider prerequisites, including authentication and any relevant 3DS setup.
• Record the expected route and compare it with the observed transaction path.

4. Test the complete outcome

Do not stop at a successful browser message. Follow the transaction through to the state recorded in the systems your operations team uses. Where results are asynchronous, define how pending transactions are recognised and followed up.

• Cover success, refusal, timeout, abandonment and pending outcomes where supported.
• Check that repeated clicks or interrupted journeys do not create unintended duplicate actions.
• Keep test evidence, unresolved issues, launch responsibilities and a rollback decision with the handover.

Official implementation references

This checklist is an independent review framework, not an API specification. Use current vendor instructions for endpoint names, fields, credentials and version-specific behaviour.

• PaymentIQ documentation (opens a new tab)
• Cashier configuration sandbox (opens a new tab)
• Hosted Fields SDK documentation (opens a new tab)
• Public Google Pay processor guide (opens a new tab)