Redirect Integration

Installment payments allow customers to split one large payment into several smaller payments over a fixed period. Opn Payments provides a set of APIs that allow you to offer your customers this convenient payment method.

How to enable

• Supported Countries: Thailand, Malaysia
• Minimum API version: 2017-11-02

To enable Installment Payments, send an email requesting this feature to support@opn.ooo. You will need to review and accept new terms and conditions.

Supported cards

Thailand

Malaysia

For installment payments made in Malaysia, merchants will absorb all interest.

Payment flow

Customers who choose to pay using installment payments go through a redirect payment flow. This means that they are redirected from your website to a external webpage to authorize and confirm the payment amount. Upon completion, the customer is redirected back to your website.

The following screenshots demonstrate this payment flow. At checkout, the customer selects the installment payment method.

After choosing the credit card with which they would like to pay, the customer is redirected to the external webpage. The payment amount and any reference numbers will already be filled out on the authorization page.

The customer has to review the information and confirm the payment. Upon confirmation, the customer will be redirected to your website via the specified return URI.

Setting who pays installment interest

One party, you (the merchant) or the customer, pays the interest for installment payments. We use the term zero-interest installments to reflect when you pay the interest instead of the customer.

Default setting

Set the default party to pay installment interest using the Dashboard. You can override this setting per charge.

Per charge setting

Override the default setting of which party pays installment interest by passing the boolean parameter zero_interest_installments at both source and charge creation. When set to true, you, the merchant, pay the interest; when set to false, the customer pays, when omitted, the default account value is used. The values passed at source and charge creation must match.

If directly charging a source, pass this parameter at charge creation.

Implementation

To create a charge using Installment Payments, make the following API requests.

1. Create a new payment source (type: installment_bay, installment_bbl, installment_first_choice, installment_kbank, installment_ktc, installment_scb, or installment_uob) using Omise.js or one of the mobile SDKs (iOS and Android)
2. Create a new charge using the identifier of the source created in Step 1.
3. After receiving the charge completion webhook event, retrieve the charge to verify its status (optional, but recommended).

Use your public key to create the Installment Payments source on the client (a customer's browser or mobile phone). Use your secret key to create the Installment Payments charge on the server.

If both the creation and charge of a source must happen server-side, you can create and charge the source in a single API request using your secret key.

Creating a source

When the customer confirms that they wish to pay with this payment method, create a new source specifying the amount, currency, installment_term, and type.

The following examples demonstrate the creation of a new Installment Payments source for ฿4,000. Replace the omise_public_key and $OMISE_PUBLIC_KEY variables with the test public key found on your dashboard.

Using Omise.js, the type parameter is supplied as the first argument to the createSource method.

Omise.setPublicKey(omise_public_key);

Omise.createSource('installment_kbank', {
  "amount": 400000,
  "currency": "THB",
  "installment_term": 4
}, function(statusCode, response) {
  console.log(response)
});

For testing, you can create the same request using curl.

curl https://api.omise.co/sources \
  -u $OMISE_PUBLIC_KEY: \
  -d "amount=400000" \
  -d "currency=THB" \
  -d "type=installment_kbank" \
  -d "installment_term=4"

{
  "object": "source",
  "id": "src_test_5xk6wi5sno7ar7p3zcv",
  "livemode": false,
  "location": "/sources/src_test_5xk6wi5sno7ar7p3zcv",
  "amount": 400000,
  "barcode": null,
  "bank": null,
  "created_at": "2023-10-26T06:03:05Z",
  "currency": "THB",
  "email": null,
  "flow": "redirect",
  "installment_term": 4,
  "ip": null,
  "absorption_type": "customer",
  "name": null,
  "mobile_number": null,
  "phone_number": null,
  "platform_type": null,
  "scannable_code": null,
  "billing": null,
  "shipping": null,
  "items": [],
  "references": null,
  "provider_references": null,
  "store_id": null,
  "store_name": null,
  "terminal_id": null,
  "type": "installment_kbank",
  "zero_interest_installments": false,
  "charge_status": "unknown",
  "receipt_amount": null,
  "discounts": []
}

The id attribute is the source identifier (begins with src).

Creating a charge

Create a charge specifying the parameters return_uri, source, amount, and currency.

• return_uri specifies the location on your website to which the customer should be redirected after completing the payment authorization step.
• source specifies the source identifier.
• amount and currency must match amount and currency of the source.

The following example demonstrates how to create a new charge using curl. Replace $OMISE_SECRET_KEY with your test secret key found on your dashboard. Replace $SOURCE_ID with the id of the source.

For installments, the following parameter may also be passed:

• zero_interest_installments, the value of which must match the value in the source.

curl https://api.omise.co/charges \
  -u $OMISE_SECRET_KEY: \
  -d "source=$SOURCE_ID" \
  -d "amount=400000" \
  -d "currency=THB" \
  -d "return_uri=https://example.com/orders/345678/complete"

{
  "object": "charge",
  "id": "chrg_test_5xk6wiaj5m45xf25q55",
  "location": "/charges/chrg_test_5xk6wiaj5m45xf25q55",
  "amount": 400000,
  "net": 384378,
  "fee": 14600,
  "fee_vat": 1022,
  "interest": 0,
  "interest_vat": 0,
  "funding_amount": 400000,
  "refunded_amount": 0,
  "transaction_fees": {
    "fee_flat": "0.0",
    "fee_rate": "3.65",
    "vat_rate": "7.0"
  },
  "platform_fee": {
    "fixed": null,
    "amount": null,
    "percentage": null
  },
  "currency": "THB",
  "funding_currency": "THB",
  "ip": null,
  "refunds": {
    "object": "list",
    "data": [],
    "limit": 20,
    "offset": 0,
    "total": 0,
    "location": "/charges/chrg_test_5xk6wiaj5m45xf25q55/refunds",
    "order": "chronological",
    "from": "1970-01-01T00:00:00Z",
    "to": "2023-10-26T06:03:06Z"
  },
  "link": null,
  "description": null,
  "metadata": {},
  "card": null,
  "source": {
    "object": "source",
    "id": "src_test_5xk6whrwrqlbqzwm3s1",
    "livemode": false,
    "location": "/sources/src_test_5xk6whrwrqlbqzwm3s1",
    "amount": 400000,
    "barcode": null,
    "bank": null,
    "created_at": "2023-10-26T06:03:03Z",
    "currency": "THB",
    "email": null,
    "flow": "redirect",
    "installment_term": 4,
    "ip": null,
    "absorption_type": "customer",
    "name": null,
    "mobile_number": null,
    "phone_number": null,
    "platform_type": null,
    "scannable_code": null,
    "billing": null,
    "shipping": null,
    "items": [],
    "references": null,
    "provider_references": null,
    "store_id": null,
    "store_name": null,
    "terminal_id": null,
    "type": "installment_kbank",
    "zero_interest_installments": false,
    "charge_status": "pending",
    "receipt_amount": null,
    "discounts": []
  },
  "schedule": null,
  "customer": null,
  "dispute": null,
  "transaction": null,
  "failure_code": null,
  "failure_message": null,
  "status": "pending",
  "authorize_uri": "https://pay.omise.co/offsites/ofsp_test_5xk6wialxdiu3oxwesy/pay",
  "return_uri": "https://example.com/orders/345678/complete",
  "created_at": "2023-10-26T06:03:06Z",
  "paid_at": null,
  "expires_at": "2023-11-02T06:03:06Z",
  "expired_at": null,
  "reversed_at": null,
  "zero_interest_installments": false,
  "branch": null,
  "terminal": null,
  "device": null,
  "authorized": false,
  "capturable": false,
  "capture": true,
  "disputable": false,
  "livemode": false,
  "refundable": false,
  "partially_refundable": false,
  "reversed": false,
  "reversible": false,
  "voided": false,
  "paid": false,
  "expired": false
}

Creating a source and charge

Alternatively, you can create and charge a source in a single API request.

curl https://api.omise.co/charges \
  -u $OMISE_SECRET_KEY: \
  -d "amount=400000" \
  -d "currency=THB" \
  -d "return_uri=http://example.com/orders/345678/complete" \
  -d "source[type]=installment_kbank" \
  -d "source[installment_term]=4"

Creating a source and charge where customer pays interest

Override the default setting of who pays installment interest by passing the zero_interest_installments parameter. See setting who pays installment interest for more details.

curl https://api.omise.co/charges \
  -u $OMISE_SECRET_KEY: \
  -d "amount=400000" \
  -d "currency=THB" \
  -d "return_uri=http://example.com/orders/345678/complete" \
  -d "zero_interest_installments=false" \
  -d "source[type]=installment_kbank" \
  -d "source[installment_term]=4"

Completing the charge

At this point, you have created a new charge with its status set to pending. Other possible values for charge status are successful, failed, and expired.

The following sections detail how to authorize a charge, receive its completion webhook event, and update its status.

Authorizing the charge

Redirect the customer to the location specified in authorize_uri so that they can authorize the charge.

The merchant can simulate this authorization phase in test mode by visiting authorize_uri to manually mark the charge as Successful or Failed.

After the customer has completed the authorization phase, they will be redirected to the location specified in return_uri.

Receiving the charge completion event

The best way to be notified about the completion of a charge is using webhook events.

Set up a location on the merchant server to receive webhook events, and add this location as a webhook endpoint on the dashboard.

Checking the charge status

After receiving this event, retrieve the charge using its id and confirm that its status matches the status of the charge contained in the event.

If the value of status is successful, you got paid.

If the value of status is failed, check the failure_code and failure_message in the charge object for an explanation.

Possible failure codes are as follows.

Voids and refunds

See the Refunds API documentation for information on how to refund an installment payment charge.

Installment payment charges cannot be partially refunded. Only full refunds are supported within 1 year of the transaction date, except for Siam Commercial Bank installments, which are refundable within 180 days.

Limits

• Minimum: 200000 (THB2,000.00)
• Maximum: 15000000 (THB150,000.00)

Since each credit card has its own monthly minimum, the effective minimum charge amount may be higher depending on the credit card and installment term length chosen.

For example, a ฿3,300 charge set to be paid over an installment term of 10 months would result a monthly charge of approximately ฿330, below the minimum for Bangkok Bank credit cards, but above the minimum for Kasikorn Bank credit cards.

Related API documentation

• Charge
• Source
• Webhook

How to check the public key and secret key

For information on how to obtain and check the public and secret keys, please refer to this document.