What it is

Carlo App is one of the payment methods available on the Core Checkout hosted payment page, alongside Card and Apple Pay. Instead of entering card details, the customer approves the payment directly from their Carlo App mobile app.

Prerequisite

• The merchant must have a Carlo App merchant account.
• The developer integrates the API and the hosted payment page as usual; the merchant chooses which payment methods to display (Card, Apple Pay, Carlo App, or any combination).

Customer flow

1. The customer goes to the merchant's site and clicks Pay.
2. The hosted payment page opens and shows the enabled methods.
3. The customer selects Carlo App.
4. The customer enters the email of their Carlo App account, or their referral code.
5. A push notification is sent to their Carlo App: a payment request from the merchant, with the amount.
6. The customer taps Pay in their Carlo App.
7. The payment confirmation is returned to the checkout page.

Test Carlo App in the sandbox, without a real account

You can test the complete Carlo App flow in the sandbox with no Carlo App account and no live payment.
In the sandbox environment, as soon as the customer selects Carlo App on the payment page, the page displays two sandbox controls, Simulate success and Simulate failure. These controls never appear in production.

How to run the test

1. Create a transaction in the sandbox and open the returned paymentPageUrl.
2. Select Carlo App.
3. Enter any value in the email or referral code field, then click Continue. In sandbox, no real account is required.
4. On the Processing Payment screen, check the transaction details: merchant, amount, transaction ID, date, and PENDING status.
5. Click Simulate success or Simulate failure.
6. Check the final screen and the redirection to your success or failure URL.

As in production, treat the callback sent to your server as the source of truth for the payment result, not the redirection.

Where the payment appears (merchant side)

A Carlo App payment shows up in two places:

• The Core Payment dashboard.
• The Carlo Business dashboard.

Refunds

Refund behaviour depends on the payment method:

Card and Apple Pay: cancelled via the API (PUT /transactions/{id}/cancel), full amount only, within 3 days.
Carlo App: a Carlo App payment is refunded only from the Carlo Business dashboard, within 30 days. It cannot be cancelled via the API, nor from the Core Payment dashboard.

A Carlo App refund made from Carlo Business does not trigger a callback, and the transaction stays COMPLETED in Core. Update the order status on your side when you refund, and report refunds made outside Core to us, as set out in the terms and conditions.

What Carlo App cannot be used for

Each Carlo App payment is approved by the customer in the app. It cannot be saved as a card, charged later by the merchant (MIT) or used for subscriptions. For these, use a bank card.

UX tip

There is currently no deep link that takes the customer straight to the pending request in the app. The request appears in the app's notifications / payment requests area, and the customer approves it there.

Fees

• Carlo App payments online use the merchant's existing Carlo App commission rate, the same one applied to in-store Carlo App payments. There's no separate online fee for Carlo App.
• The Card / Apple Pay fee only applies if those methods are activated as well.

Updated on: 28/10/2026