Select payment method
This endpoint creates a new payment session with the customer's chosen payment method. It returns a payment session ID that you'll use in subsequent API calls to complete the payment flow.
The flow after calling this endpoint depends on the selected payment method:
- For card payments: You must provide a card token obtained from
tokenize-card, or a saved card's token right afterrehydrate-card - For QR code payments: Call
retrieve-qr-datato get the QR code data to display - For redirect-based payments: Call
get-redirect-urlto get the URL to redirect the customer to
Card installments:
To charge a card in monthly installments instead of a single payment, pass an
installment_plan_id obtained from list-installment-plans. The amount and currency
must match the values you passed to list-installment-plans, and the card you tokenize
must be the card whose BIN (or token) you used there, so the chosen plan stays eligible
and the customer's quote remains consistent. Omit installment_plan_id to charge the card
as a one-time payment.
Billing-address fields are routed according to the setting that requires them:
| Configuration | Address destination | Required fields |
|---|---|---|
Card payment method requires_address: true |
tokenize-card |
The card payment method's required_fields |
Installation address_capture: required |
select-payment-method |
The selected payment method's required_fields |
Address fields required by the selected payment method must be submitted to this endpoint.
An empty required_fields configuration uses the default full address consisting of
street_address_1, postal_code, city, state, and country; street_address_2 is
always optional.
After starting the payment flow, you should poll discover-next-action to track the payment status
and determine the next steps.
merchant_id
string
Required. Your merchant ID that uniquely identifies your account.
installation_id
string
Required. The installation ID for this platform (e.g. your iOS app, Android app, website, or terminal).
installment_plan_id
string
Optional. For card installment payments only: the plan ID chosen from list-installment-plans. Omit for one-time card payments.
amount
string
Required. The payment amount in the smallest currency unit (e.g. cents). Must be a positive integer.
currency
string
Required. The three-letter ISO currency code (e.g. THB). Must match the funding currency configured for your provider.
payment_method
string
Required. The payment method code (e.g. CARD, PROMPTPAY, K_PLUS). Must be enabled for your account.
token
string
Optional. For card payments only: The card token obtained from tokenize-card. For a saved card, pass its token right after calling rehydrate-card with the customer's security code. Required when payment_method is CARD.
customer_email
string
Optional. Customer's email address. Required if the installation is configured to require email capture.
customer_mobile
string
Optional. Customer's mobile phone number. Required if the installation is configured to require mobile capture.
customer_name
string
Optional. Customer's name.
customer_language
string
Optional. Customer's preferred language for communications. Defaults to en when omitted.
enth
interest_bearer
string
Optional. Who bears the installment interest: customer or merchant. When omitted, the merchant's configured default is used; if the merchant has no default configured this argument is required. Must match the value passed to list-installment-plans so the customer's displayed quote matches the locked snapshot. Ignored when installment_plan_id is omitted.
customermerchant
street_address_1
string
Optional. The first line of the address (e.g. street number and name).
street_address_2
string
Optional. The second line of the address (e.g. apartment, suite, or unit).
postal_code
string
Optional. The postal or ZIP code of the address.
city
string
Optional. The city of the address.
state
string
Optional. The state, province, or region of the address.
country
string
Optional. The country of the address.
INVALID_ARGUMENTS
This error occurs when the request contains invalid or missing parameters. Common cases include:
- A missing
merchant_id,installation_id,amount,currency, orpayment_method - An unsupported
currency(must match the funding currency configured for your provider) - An installation that could not be found or does not have the requested payment method enabled
- Missing customer email or mobile when required by the installation
- Missing address fields when required by the installation and payment method
NOT_FOUND
This error occurs when we cannot find the merchant account, installation, or card token with the IDs provided. Double check that you are using the correct IDs.
TOKEN_ALREADY_USED
This single-use token has already been used to create a payment session. Each single-use token can only be used once. Request a new token from tokenize-card.
NOT_ENABLED
This installation is currently disabled.
INSTALLMENT_NOT_ELIGIBLE
The installment plan you provided is no longer available for this amount/card combination. Re-fetch eligible plans via list-installment-plans and try again.
UNHANDLED_ERROR
This error occurs when the server encounters an unexpected internal error that it cannot handle gracefully. This typically happens due to bugs, infrastructure issues, or edge cases that weren't anticipated during development.
INVALID_ARGUMENTS
This error occurs when the request contains invalid or missing parameters. Common cases include missing required fields, or values that don't match the expected format or type.
BAD_VERSION
This error occurs when making requests to an API version that is either deprecated or not yet released. This commonly happens when using an outdated SDK or when the API version specified in the request URL is incorrect.
curl "https://api.reservepay.com/sdk/select-payment-method" \
-X POST
-H "Content-Type: application/json" \
-H "Accept: application/json" \
-d '{
"merchant_id": "123456789012",
"installation_id": "ins_xhBi6ypq9G",
"amount": 100000,
"currency": "THB",
"payment_method": "CARD",
"token": "IC3949UCOE6U93"
}'