Initiate a PayIn Transaction

The Initiate PayIn endpoint starts a new payment transaction on behalf of your customer. On success, it returns a transaction_id you should persist for status checks and a checkout_url to which you redirect the customer to complete the payment. The Transaction API supports multiple payment types (from QR and UPI Intent to cards and net banking), giving you fine-grained control over the checkout experience.

Quick ReferenceMethod: POSTRequired: amount, merchant_ref_id, customer_info, payment_type, plus fingerprint headersReturns: transaction_id, checkout_urlMinimum amount: ₹200Payment types: QR, UPI Intent, Cards, Net Banking

Endpoint

POST https://api.fastflowpe.com/merchant/payin/initialize

The minimum transaction amount is ₹200. Requests with a lower amount will be rejected.

Headers

string

required

Your merchant API key, provided by FastFlowPe.

string

required

Must be application/json.

string

required

The browser or device user agent string of the customer’s client. Pass the actual user agent from the customer’s request where possible.

string

required

Base64-encoded browser or device fingerprint. Used for fraud detection and transaction validation.

string

required

The platform from which the request originates. Accepted values: web, mobile, app.

string

required

The version of your client application (e.g. 10).

Body Parameters

string

required

The payment method to use for this transaction. Accepted values: QR, INTENT, CREDIT_CARD, DEBIT_CARD, NETBANKING, EMI, PAYLATER.

float

required

Amount to charge the customer, in Indian Rupees. Minimum value is ₹200.

string

required

Unique identifier for the order on your system. Must be unique per transaction.

string

required

A description of the product or transaction. Must be at least 8 characters long.

object

required

An object containing the customer’s contact details.

Show customer_info fields

string

required

Full name of the customer.

string

required

Email address of the customer.

string

required

10-digit mobile number of the customer, without country code.

string

Operating system of the customer’s device. Required when payment_type is INTENT or QR. Accepted values: IOS, ANDROID.

string

The UPI app to deep-link the customer into. Required when payment_type is INTENT or QR. Accepted values: PHONEPE, GPAY, PAYTM, CRED, BHIM, AMAZON. Omit this field to request a generic Intent URL (supported on Android only).

string

The customer’s UPI ID for direct UPI collect flows. Optional.

curl --location 'https://api.fastflowpe.com/merchant/payin/initialize' \
--header 'x-api-key: <your-api-key>' \
--header 'Content-Type: application/json' \
--header 'user-agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)' \
--header 'x-browser-fingerprint: TW96aWxsYS81LjAgKE1hY2lud' \
--header 'x-source-channel: web' \
--header 'x-source-channel-version: 10' \
--data-raw '{
    "order_id": "ORD123456789",
    "amount": 500,
    "payment_type": "INTENT",
    "device_os": "IOS",
    "target_app": "PHONEPE",
    "productinfo": "Premium Subscription",
    "customer_info": {
        "name": "John Doe",
        "email": "john@example.com",
        "phone_number": "9999999999"
    }
}'

import requests

url = "https://api.fastflowpe.com/merchant/payin/initialize"
headers = {
    "x-api-key": "<your-api-key>",
    "Content-Type": "application/json",
    "user-agent": "Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)",
    "x-browser-fingerprint": "TW96aWxsYS81LjAgKE1hY2lud",
    "x-source-channel": "web",
    "x-source-channel-version": "10",
}
payload = {
    "order_id": "ORD123456789",
    "amount": 500,
    "payment_type": "INTENT",
    "device_os": "IOS",
    "target_app": "PHONEPE",
    "productinfo": "Premium Subscription",
    "customer_info": {
        "name": "John Doe",
        "email": "john@example.com",
        "phone_number": "9999999999",
    },
}

response = requests.post(url, json=payload, headers=headers)
print(response.json())

const response = await fetch("https://api.fastflowpe.com/merchant/payin/initialize", {
  method: "POST",
  headers: {
    "x-api-key": "<your-api-key>",
    "Content-Type": "application/json",
    "user-agent": "Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)",
    "x-browser-fingerprint": "TW96aWxsYS81LjAgKE1hY2lud",
    "x-source-channel": "web",
    "x-source-channel-version": "10",
  },
  body: JSON.stringify({
    order_id: "ORD123456789",
    amount: 500,
    payment_type: "INTENT",
    device_os: "IOS",
    target_app: "PHONEPE",
    productinfo: "Premium Subscription",
    customer_info: {
      name: "John Doe",
      email: "john@example.com",
      phone_number: "9999999999",
    },
  }),
});
console.log(await response.json());

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

String body = """
{
  "order_id": "ORD123456789",
  "amount": 500,
  "payment_type": "INTENT",
  "device_os": "IOS",
  "target_app": "PHONEPE",
  "productinfo": "Premium Subscription",
  "customer_info": {
    "name": "John Doe",
    "email": "john@example.com",
    "phone_number": "9999999999"
  }
}
""";

HttpClient client = HttpClient.newHttpClient();
HttpRequest request = HttpRequest.newBuilder()
    .uri(URI.create("https://api.fastflowpe.com/merchant/payin/initialize"))
    .header("x-api-key", "<your-api-key>")
    .header("Content-Type", "application/json")
    .header("user-agent", "Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)")
    .header("x-browser-fingerprint", "TW96aWxsYS81LjAgKE1hY2lud")
    .header("x-source-channel", "web")
    .header("x-source-channel-version", "10")
    .POST(HttpRequest.BodyPublishers.ofString(body))
    .build();

HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
System.out.println(response.body());

package main

import (
    "bytes"
    "fmt"
    "io"
    "net/http"
)

func main() {
    payload := []byte(`{
        "order_id": "ORD123456789",
        "amount": 500,
        "payment_type": "INTENT",
        "device_os": "IOS",
        "target_app": "PHONEPE",
        "productinfo": "Premium Subscription",
        "customer_info": {"name": "John Doe", "email": "john@example.com", "phone_number": "9999999999"}
    }`)

    req, _ := http.NewRequest("POST", "https://api.fastflowpe.com/merchant/payin/initialize", bytes.NewBuffer(payload))
    req.Header.Set("x-api-key", "<your-api-key>")
    req.Header.Set("Content-Type", "application/json")
    req.Header.Set("user-agent", "Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)")
    req.Header.Set("x-browser-fingerprint", "TW96aWxsYS81LjAgKE1hY2lud")
    req.Header.Set("x-source-channel", "web")
    req.Header.Set("x-source-channel-version", "10")

    resp, _ := http.DefaultClient.Do(req)
    defer resp.Body.Close()
    body, _ := io.ReadAll(resp.Body)
    fmt.Println(string(body))
}

<?php
$payload = json_encode([
    "order_id" => "ORD123456789",
    "amount" => 500,
    "payment_type" => "INTENT",
    "device_os" => "IOS",
    "target_app" => "PHONEPE",
    "productinfo" => "Premium Subscription",
    "customer_info" => [
        "name" => "John Doe",
        "email" => "john@example.com",
        "phone_number" => "9999999999",
    ],
]);

$ch = curl_init("https://api.fastflowpe.com/merchant/payin/initialize");
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    "x-api-key: <your-api-key>",
    "Content-Type: application/json",
    "user-agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)",
    "x-browser-fingerprint: TW96aWxsYS81LjAgKE1hY2lud",
    "x-source-channel: web",
    "x-source-channel-version: 10",
]);
$response = curl_exec($ch);
curl_close($ch);
echo $response;

require 'net/http'
require 'uri'
require 'json'

uri = URI('https://api.fastflowpe.com/merchant/payin/initialize')
request = Net::HTTP::Post.new(uri)
request['x-api-key'] = '<your-api-key>'
request['Content-Type'] = 'application/json'
request['user-agent'] = 'Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)'
request['x-browser-fingerprint'] = 'TW96aWxsYS81LjAgKE1hY2lud'
request['x-source-channel'] = 'web'
request['x-source-channel-version'] = '10'
request.body = {
  order_id: 'ORD123456789',
  amount: 500,
  payment_type: 'INTENT',
  device_os: 'IOS',
  target_app: 'PHONEPE',
  productinfo: 'Premium Subscription',
  customer_info: {
    name: 'John Doe',
    email: 'john@example.com',
    phone_number: '9999999999',
  },
}.to_json

response = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |http| http.request(request) }
puts response.body

Responses

{
  "status": "success",
  "status_code": 200,
  "message": "Payin Initiated Successfully",
  "detail": null,
  "data": {
    "transaction_id": "1be74773-88ca-48db-afa6-243d26e29375",
    "checkout_url": "https://checkout.fastflowpe.com/pay/tx_8fj39dk29slx7ab"
  },
  "meta": null
}

{
  "status": "error",
  "status_code": "4xx",
  "message": "<reason for failure>",
  "detail": "<additional detail or null>",
  "data": null,
  "meta": null
}

Redirect your customer to the checkout_url immediately after receiving a success response. Save the transaction_id — you will need it to poll the Check Transaction Status endpoint and confirm the payment outcome.

⌘I

curl --location 'https://api.fastflowpe.com/merchant/payin/initialize' \
--header 'x-api-key: <your-api-key>' \
--header 'Content-Type: application/json' \
--header 'user-agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)' \
--header 'x-browser-fingerprint: TW96aWxsYS81LjAgKE1hY2lud' \
--header 'x-source-channel: web' \
--header 'x-source-channel-version: 10' \
--data-raw '{
    "order_id": "ORD123456789",
    "amount": 500,
    "payment_type": "INTENT",
    "device_os": "IOS",
    "target_app": "PHONEPE",
    "productinfo": "Premium Subscription",
    "customer_info": {
        "name": "John Doe",
        "email": "john@example.com",
        "phone_number": "9999999999"
    }
}'

import requests

url = "https://api.fastflowpe.com/merchant/payin/initialize"
headers = {
    "x-api-key": "<your-api-key>",
    "Content-Type": "application/json",
    "user-agent": "Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)",
    "x-browser-fingerprint": "TW96aWxsYS81LjAgKE1hY2lud",
    "x-source-channel": "web",
    "x-source-channel-version": "10",
}
payload = {
    "order_id": "ORD123456789",
    "amount": 500,
    "payment_type": "INTENT",
    "device_os": "IOS",
    "target_app": "PHONEPE",
    "productinfo": "Premium Subscription",
    "customer_info": {
        "name": "John Doe",
        "email": "john@example.com",
        "phone_number": "9999999999",
    },
}

response = requests.post(url, json=payload, headers=headers)
print(response.json())

const response = await fetch("https://api.fastflowpe.com/merchant/payin/initialize", {
  method: "POST",
  headers: {
    "x-api-key": "<your-api-key>",
    "Content-Type": "application/json",
    "user-agent": "Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)",
    "x-browser-fingerprint": "TW96aWxsYS81LjAgKE1hY2lud",
    "x-source-channel": "web",
    "x-source-channel-version": "10",
  },
  body: JSON.stringify({
    order_id: "ORD123456789",
    amount: 500,
    payment_type: "INTENT",
    device_os: "IOS",
    target_app: "PHONEPE",
    productinfo: "Premium Subscription",
    customer_info: {
      name: "John Doe",
      email: "john@example.com",
      phone_number: "9999999999",
    },
  }),
});
console.log(await response.json());

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

String body = """
{
  "order_id": "ORD123456789",
  "amount": 500,
  "payment_type": "INTENT",
  "device_os": "IOS",
  "target_app": "PHONEPE",
  "productinfo": "Premium Subscription",
  "customer_info": {
    "name": "John Doe",
    "email": "john@example.com",
    "phone_number": "9999999999"
  }
}
""";

HttpClient client = HttpClient.newHttpClient();
HttpRequest request = HttpRequest.newBuilder()
    .uri(URI.create("https://api.fastflowpe.com/merchant/payin/initialize"))
    .header("x-api-key", "<your-api-key>")
    .header("Content-Type", "application/json")
    .header("user-agent", "Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)")
    .header("x-browser-fingerprint", "TW96aWxsYS81LjAgKE1hY2lud")
    .header("x-source-channel", "web")
    .header("x-source-channel-version", "10")
    .POST(HttpRequest.BodyPublishers.ofString(body))
    .build();

HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
System.out.println(response.body());

package main

import (
    "bytes"
    "fmt"
    "io"
    "net/http"
)

func main() {
    payload := []byte(`{
        "order_id": "ORD123456789",
        "amount": 500,
        "payment_type": "INTENT",
        "device_os": "IOS",
        "target_app": "PHONEPE",
        "productinfo": "Premium Subscription",
        "customer_info": {"name": "John Doe", "email": "john@example.com", "phone_number": "9999999999"}
    }`)

    req, _ := http.NewRequest("POST", "https://api.fastflowpe.com/merchant/payin/initialize", bytes.NewBuffer(payload))
    req.Header.Set("x-api-key", "<your-api-key>")
    req.Header.Set("Content-Type", "application/json")
    req.Header.Set("user-agent", "Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)")
    req.Header.Set("x-browser-fingerprint", "TW96aWxsYS81LjAgKE1hY2lud")
    req.Header.Set("x-source-channel", "web")
    req.Header.Set("x-source-channel-version", "10")

    resp, _ := http.DefaultClient.Do(req)
    defer resp.Body.Close()
    body, _ := io.ReadAll(resp.Body)
    fmt.Println(string(body))
}

<?php
$payload = json_encode([
    "order_id" => "ORD123456789",
    "amount" => 500,
    "payment_type" => "INTENT",
    "device_os" => "IOS",
    "target_app" => "PHONEPE",
    "productinfo" => "Premium Subscription",
    "customer_info" => [
        "name" => "John Doe",
        "email" => "john@example.com",
        "phone_number" => "9999999999",
    ],
]);

$ch = curl_init("https://api.fastflowpe.com/merchant/payin/initialize");
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    "x-api-key: <your-api-key>",
    "Content-Type: application/json",
    "user-agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)",
    "x-browser-fingerprint: TW96aWxsYS81LjAgKE1hY2lud",
    "x-source-channel: web",
    "x-source-channel-version: 10",
]);
$response = curl_exec($ch);
curl_close($ch);
echo $response;

require 'net/http'
require 'uri'
require 'json'

uri = URI('https://api.fastflowpe.com/merchant/payin/initialize')
request = Net::HTTP::Post.new(uri)
request['x-api-key'] = '<your-api-key>'
request['Content-Type'] = 'application/json'
request['user-agent'] = 'Mozilla/5.0 (iPhone; CPU iPhone OS 18_5 like Mac OS X)'
request['x-browser-fingerprint'] = 'TW96aWxsYS81LjAgKE1hY2lud'
request['x-source-channel'] = 'web'
request['x-source-channel-version'] = '10'
request.body = {
  order_id: 'ORD123456789',
  amount: 500,
  payment_type: 'INTENT',
  device_os: 'IOS',
  target_app: 'PHONEPE',
  productinfo: 'Premium Subscription',
  customer_info: {
    name: 'John Doe',
    email: 'john@example.com',
    phone_number: '9999999999',
  },
}.to_json

response = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |http| http.request(request) }
puts response.body

{
  "status": "success",
  "status_code": 200,
  "message": "Payin Initiated Successfully",
  "detail": null,
  "data": {
    "transaction_id": "1be74773-88ca-48db-afa6-243d26e29375",
    "checkout_url": "https://checkout.fastflowpe.com/pay/tx_8fj39dk29slx7ab"
  },
  "meta": null
}

{
  "status": "error",
  "status_code": "4xx",
  "message": "<reason for failure>",
  "detail": "<additional detail or null>",
  "data": null,
  "meta": null
}

Get Started

Collections

Payment Links

Fund Transfer

Refunds

Callbacks

Initiate a PayIn Transaction

Endpoint

Headers

Body Parameters

Responses

​Endpoint

​Headers

​Body Parameters

​Responses

Endpoint

Headers

Body Parameters

Responses