curl --request POST \
  --url https://sandbox.cashfree.com/pg/subscriptions/{subscription_id}/refunds \
  --header 'Content-Type: application/json' \
  --header 'x-api-version: <x-api-version>' \
  --header 'x-client-id: <api-key>' \
  --header 'x-client-secret: <api-key>' \
  --data '
{
  "subscription_id": "test-subs-id",
  "payment_id": "test-payment-id",
  "refund_id": "dummy-test-refund-id",
  "refund_amount": 10,
  "refund_note": "full refund",
  "refund_speed": "INSTANT"
}
'

import requests

url = "https://sandbox.cashfree.com/pg/subscriptions/{subscription_id}/refunds"

payload = {
    "subscription_id": "test-subs-id",
    "payment_id": "test-payment-id",
    "refund_id": "dummy-test-refund-id",
    "refund_amount": 10,
    "refund_note": "full refund",
    "refund_speed": "INSTANT"
}
headers = {
    "x-api-version": "<x-api-version>",
    "x-client-id": "<api-key>",
    "x-client-secret": "<api-key>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {
    'x-api-version': '<x-api-version>',
    'x-client-id': '<api-key>',
    'x-client-secret': '<api-key>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    subscription_id: 'test-subs-id',
    payment_id: 'test-payment-id',
    refund_id: 'dummy-test-refund-id',
    refund_amount: 10,
    refund_note: 'full refund',
    refund_speed: 'INSTANT'
  })
};

fetch('https://sandbox.cashfree.com/pg/subscriptions/{subscription_id}/refunds', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://sandbox.cashfree.com/pg/subscriptions/{subscription_id}/refunds",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'subscription_id' => 'test-subs-id',
    'payment_id' => 'test-payment-id',
    'refund_id' => 'dummy-test-refund-id',
    'refund_amount' => 10,
    'refund_note' => 'full refund',
    'refund_speed' => 'INSTANT'
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "x-api-version: <x-api-version>",
    "x-client-id: <api-key>",
    "x-client-secret: <api-key>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

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

func main() {

	url := "https://sandbox.cashfree.com/pg/subscriptions/{subscription_id}/refunds"

	payload := strings.NewReader("{\n  \"subscription_id\": \"test-subs-id\",\n  \"payment_id\": \"test-payment-id\",\n  \"refund_id\": \"dummy-test-refund-id\",\n  \"refund_amount\": 10,\n  \"refund_note\": \"full refund\",\n  \"refund_speed\": \"INSTANT\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("x-api-version", "<x-api-version>")
	req.Header.Add("x-client-id", "<api-key>")
	req.Header.Add("x-client-secret", "<api-key>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://sandbox.cashfree.com/pg/subscriptions/{subscription_id}/refunds")
  .header("x-api-version", "<x-api-version>")
  .header("x-client-id", "<api-key>")
  .header("x-client-secret", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"subscription_id\": \"test-subs-id\",\n  \"payment_id\": \"test-payment-id\",\n  \"refund_id\": \"dummy-test-refund-id\",\n  \"refund_amount\": 10,\n  \"refund_note\": \"full refund\",\n  \"refund_speed\": \"INSTANT\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://sandbox.cashfree.com/pg/subscriptions/{subscription_id}/refunds")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["x-api-version"] = '<x-api-version>'
request["x-client-id"] = '<api-key>'
request["x-client-secret"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"subscription_id\": \"test-subs-id\",\n  \"payment_id\": \"test-payment-id\",\n  \"refund_id\": \"dummy-test-refund-id\",\n  \"refund_amount\": 10,\n  \"refund_note\": \"full refund\",\n  \"refund_speed\": \"INSTANT\"\n}"

response = http.request(request)
puts response.read_body

{
  "payment_id": "pay8643",
  "cf_payment_id": "863782648",
  "refund_id": "refund2",
  "cf_refund_id": "ref_212",
  "refund_amount": 100,
  "refund_note": "test",
  "refund_speed": "INSTANT",
  "refund_status": "INITIATED"
}

{
  "message": "bad URL, please check API documentation",
  "code": "request_failed",
  "type": "invalid_request_error"
}

{
  "message": "authentication Failed",
  "code": "request_failed",
  "type": "authentication_error"
}

{
  "message": "something is not found",
  "code": "somethind_not_found",
  "type": "invalid_request_error"
}

{
  "message": "something is not found",
  "code": "request_invalid",
  "type": "idempotency_error"
}

{
  "message": "Too many requests from IP. Check headers",
  "code": "request_failed",
  "type": "rate_limit_error"
}

{
  "message": "internal Server Error",
  "code": "internal_error",
  "type": "api_error"
}