Quick Answer: Integrating PayNow payments via API in Singapore requires connecting to a licensed payment gateway that supports the paynow_online payment method, generating payment requests or static QR codes, and handling webhook confirmations for settlement. HitPay (MAS licence PS20200643) provides a REST API that enables Singapore merchants to accept PayNow alongside GrabPay, ShopeePay, cards, and 50+ other payment methods — with next business day SGD payouts for domestic transactions.

Singapore's PayNow network has made instant bank-to-bank transfers the default expectation for digital payments. According to Statista Singapore e-commerce data, Singapore's e-commerce market continues to grow rapidly, and PayNow acceptance is now a baseline requirement for online stores, service businesses, and F&B operators alike.

For merchants who want PayNow embedded directly into their checkout flow — rather than relying on a payment link — API integration is the correct approach. This guide covers the technical path and the practical decisions that come with it.

What does a PayNow API integration actually involve?

At its core, a PayNow API integration involves three steps: creating a payment request, displaying a QR code or redirect for the customer, and confirming payment via webhook.

Most payment gateways expose a REST API where merchants send a POST request with the payment amount, currency (SGD), and the payment method identifier — typically paynow_online. The API returns a QR code value or a hosted checkout URL. The customer scans the QR using any Singapore banking app, and the gateway fires a webhook to the merchant's server when payment is confirmed.

The Monetary Authority of Singapore (MAS) requires that payment gateways handling PayNow transactions hold a valid Payment Services licence. Merchants should verify that any gateway they integrate with is MAS-licensed before going live — unlicensed intermediaries carry compliance and settlement risk.

What are the two main API patterns for PayNow?

Dynamic payment requests

A dynamic payment request generates a unique QR code for each transaction, tied to a specific amount. This is the standard pattern for e-commerce checkouts. The merchant creates a payment request via API, receives a QR value and a hosted checkout URL, and redirects the customer or embeds the QR on the checkout page.

This approach supports automated reconciliation: each payment is linked to a unique reference number, making it straightforward to match payments to orders in a database.

Static QR codes

A static QR code is generated once and displayed permanently — at a retail counter, printed on a menu, or embedded in a PDF invoice. If no amount is pre-set, the customer enters it manually.

Using HitPay's API, a static QR is created via POST /v1/static_qr with the paynow_online payment method specified. The response includes a qr_value field containing the raw QR string, which merchants render into a scannable code. An optional location_id parameter tags all transactions to a specific outlet — useful for businesses operating across multiple locations such as a Tiong Bahru café and an Orchard Road flagship.

The trade-off: static QRs require manual reconciliation since they are not tied to specific transaction amounts.

How do webhooks work for PayNow confirmation?

PayNow transactions are asynchronous. The customer scans and pays, but the confirmation event reaches the merchant's server via webhook — not through a synchronous API response.

HitPay's webhook system sends a POST request to a registered endpoint when a payment is completed. The payload includes the payment status, payment ID, and reference number. Merchants must verify the HMAC-SHA256 signature using their API salt before processing the confirmation.

The current best practice is to register the webhook URL in the dashboard (Developers > Webhook Endpoints) rather than passing it as a parameter in the payment request — the inline webhook parameter is deprecated and will be removed in a future API version.

For local development without a public URL, polling the payment status endpoint (GET /v1/payment-requests/{id}) every 3 seconds is an acceptable fallback. For production, webhooks are required.

API rate limits to know: - General API: 400 requests per minute - Payment request endpoint: 70 requests per minute

Polling in production can exhaust these limits quickly — another reason webhooks are the correct architecture.

What integration options exist for non-developers?

Not every Singapore merchant needs a custom API build. Several no-code and low-code paths exist:

1. Payment links — HitPay's payment links enable PayNow acceptance via a shareable URL, suitable for WhatsApp, Instagram DMs, and email invoices. No API required. As covered in the guide to generating free payment links in Singapore, this is the fastest path to live PayNow acceptance.

2. Drop-In UI (HitPay.JS) — HitPay's drop-in checkout UI embeds a hosted checkout component directly into a webpage with minimal JavaScript. PayNow, GrabPay, ShopeePay, and cards are all rendered automatically based on the merchant's enabled methods.

3. Platform plugins — WooCommerce, Shopify, and Wix plugins connect PayNow without any API code. The online payment methods guide for Singapore outlines which platforms each plugin supports.

4. Custom API — For bespoke checkout flows, recurring billing, or multi-channel reconciliation, direct API integration using HitPay's REST endpoints is the appropriate path.

How does HitPay handle PayNow API integration?

HitPay's API supports both dynamic payment requests and static QR generation for paynow_online. The same integration surfaces PayNow alongside GrabPay, ShopeePay, Atome, Shopee PayLater, and cards — merchants do not need separate integrations per method.

For Singapore merchants, domestic PayNow transactions settle next business day in SGD. Cross-border payments — from international customers using PromptPay (Thailand), DuitNow (Malaysia), QRIS (Indonesia), UPI (India), or WeChat Pay (China) — settle at T+2.

HitPay is PCI DSS compliant and holds MAS licence PS20200643. Sign-up is free, with no monthly fees or setup costs. Approval typically completes within 1–3 business days. Sandbox credentials are available immediately for development and testing.

For merchants building a custom integration, the correct sequence is:

1. Register for a HitPay sandbox account at dashboard.sandbox.hit-pay.com

2. Retrieve the API key and salt from Developers > Webhook Endpoints

3. Build and test payment request or static QR creation in sandbox

4. Configure a webhook endpoint and verify HMAC signature handling

5. Switch API base URL to https://api.hit-pay.com/v1/ and update credentials for production

6. Complete PayNow and any additional payment method setup in the production dashboard

Frequently Asked Questions