API Reference

Authentication

Pass your API key in the x-api-key header on every request to authenticated endpoints.

x-api-key: sk_paynow_YOUR_SECRET_KEY

Key Types

Secret keys must never be exposed in client-side code. Use publishable keys with domain restrictions for browser integrations.

POST /api/v1/generate

Generate a PayNow QR code. Returns the raw QR string, image URLs, and optionally a WhatsApp link. Requires API key.

Request Parameters

Response

{
  "qr_string": "00020101021226370009SG.PAYNOW...",
  "image_url": "https://paynow.doubleam.com/api/v1/qr.png?...",
  "card_url": "https://paynow.doubleam.com/api/v1/card.png?...",
  "whatsapp_url": "https://wa.me/6591234567?text=...",
  "payment": {
    "paymentType": "uen",
    "proxy": "202521700C",
    "amount": "10.50",
    "editable": false,
    "merchantName": "My Business",
    "reference": "INV-001",
    "expiry": null,
    "currency": "SGD",
    "static": false
  }
}

whatsapp_url is only present when whatsapp_to is provided. static is true when no amount is set (reusable QR).

GET /api/v1/card.png

Returns a branded PayNow card as a PNG image. Public endpoint — no API key required. This is what WhatsApp, email clients, and browsers fetch.

Query Parameters

Same as /generate: payment_type, uen/mobile, amount, merchant_name, reference, size.

Response

Content-Type: image/png — raw PNG bytes. Use the URL directly in <img> tags or WhatsApp template headers.

curl "https://paynow.doubleam.com/api/v1/card.png?payment_type=uen&uen=202521700C&amount=10.50&merchant_name=TEST" \
  -o card.png

GET /api/v1/qr.png

Returns a plain QR code PNG (no branding). Public endpoint.

Same query parameters as /card.png. Use when you need a raw QR without the branded card layout.

GET /api/v1/records

List payment requests generated with your API key. Requires API key. Use this to pull records into your own system for reconciliation.

Query Parameters

Response

{
  "records": [
    {
      "id": "uuid",
      "payment_type": "uen",
      "proxy": "202521700C",
      "amount": "10.50",
      "merchant_name": "My Business",
      "reference": "INV-001",
      "created_at": "2026-06-27T12:00:00.000Z"
    }
  ],
  "limit": 20,
  "offset": 0
}

GET /health

Liveness check. Public, no auth.

{ "ok": true, "service": "doubleam-paynow-api", "version": "2.0.0" }

Reference Behaviour

The reference field in the QR encodes a bill/invoice number (max 25 chars) that the payer's bank app may display. Three modes:

The card displays exactly the reference value that is encoded in the QR (up to 25 characters). There is no display/encode mismatch.

Errors

All errors return JSON with error and message fields.

429 Rate Limit Response

{
  "error": "rate_limited",
  "message": "Monthly limit exceeded (50/50). Upgrade your plan for more requests.",
  "usage": { "used": 50, "limit": 50 }
}

Rate Limits

The GET /records endpoint does not count toward the monthly quota. When the quota is exceeded, the API returns 429 with a JSON body showing current usage.

Code Examples

curl

curl -X POST https://paynow.doubleam.com/api/v1/generate \
  -H "Content-Type: application/json" \
  -H "x-api-key: sk_paynow_YOUR_KEY" \
  -d '{
    "payment_type": "uen",
    "uen": "202521700C",
    "amount": "150.00",
    "merchant_name": "Acme Pte Ltd",
    "reference": "INV-2026-042"
  }'

Node.js (fetch)

const response = await fetch("https://paynow.doubleam.com/api/v1/generate", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "x-api-key": "sk_paynow_YOUR_KEY",
  },
  body: JSON.stringify({
    payment_type: "uen",
    uen: "202521700C",
    amount: "150.00",
    merchant_name: "Acme Pte Ltd",
    reference: "INV-2026-042",
  }),
});

const data = await response.json();
console.log(data.card_url);   // branded card image URL
console.log(data.qr_string);  // raw EMVCo payload

Python (requests)

import requests

resp = requests.post(
    "https://paynow.doubleam.com/api/v1/generate",
    headers={"x-api-key": "sk_paynow_YOUR_KEY"},
    json={
        "payment_type": "uen",
        "uen": "202521700C",
        "amount": "150.00",
        "merchant_name": "Acme Pte Ltd",
        "reference": "INV-2026-042",
    },
)

data = resp.json()
print(data["card_url"])   # branded card image URL
print(data["qr_string"])  # raw EMVCo payload

PHP

$ch = curl_init("https://paynow.doubleam.com/api/v1/generate");
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        "Content-Type: application/json",
        "x-api-key: sk_paynow_YOUR_KEY",
    ],
    CURLOPT_POSTFIELDS => json_encode([
        "payment_type" => "uen",
        "uen" => "202521700C",
        "amount" => "150.00",
        "merchant_name" => "Acme Pte Ltd",
        "reference" => "INV-2026-042",
    ]),
]);

$response = curl_exec($ch);
curl_close($ch);

$data = json_decode($response, true);
echo $data["card_url"];   // branded card image URL
echo $data["qr_string"];  // raw EMVCo payload

OpenAPI Spec

The full OpenAPI 3.1 specification is available for generating client SDKs and importing into API tools like Postman or Insomnia.