How UPI Works – Complete Guide
Everything about India's Unified Payments Interface: UPI IDs, QR format, apps and global expansion.
What is UPI?
UPI — the Unified Payments Interface — is India's national real-time payment system, developed and operated by the National Payments Corporation of India (NPCI) under the oversight of the Reserve Bank of India (RBI). Launched in April 2016, UPI has grown into the world's largest instant payment network by transaction volume, processing over 10 billion transactions per month as of 2026.
UPI allows any two bank account holders in India to transfer money instantly, 24 hours a day, 7 days a week — including bank holidays — at zero cost to consumers. Instead of requiring account numbers and IFSC codes, UPI uses a simple address called a Virtual Payment Address (VPA) or UPI ID in the format username@bankhandle.
Today, over 500 banks and dozens of consumer apps participate in the UPI ecosystem. India accounts for approximately 46% of all real-time payment transactions globally — more than the US, EU and China combined — largely thanks to UPI.
How UPI Works – Step by Step
- 1
Merchant displays UPI QR code
A static QR code (for any amount) is printed or displayed at the counter. For invoices and e-commerce, a dynamic QR with the exact amount is generated per transaction.
- 2
Customer opens any UPI app
PhonePe, Google Pay, Paytm, BHIM, Amazon Pay, WhatsApp Pay or any banking app work identically. UPI is fully interoperable across all participating apps and banks.
- 3
Customer scans the QR code
The app activates the camera. The UPI QR can be scanned from a printed slip, a phone screen or a digital PDF – any surface works.
- 4
Payment details are pre-filled
The payee UPI ID, name, and amount (if embedded in the QR) are instantly extracted. No manual entry, no typos, no wrong IFSC codes.
- 5
Customer enters UPI PIN
The 4- or 6-digit UPI PIN is the final authentication step. It never leaves the device and is never stored anywhere outside the bank's secure system.
- 6
Transfer completes within seconds
The NPCI infrastructure processes the transfer in real time. Funds move directly between bank accounts – no intermediary wallet involved.
- 7
Both parties receive confirmation
The payer gets a transaction success notification. The payee receives an instant credit alert via SMS and in-app notification. The transaction ID is shared for reference.
Understanding UPI IDs
A UPI ID (Virtual Payment Address / VPA) is the human-readable address of a bank account in the UPI system. The format is always username@bankhandle. The username part can be a mobile number, name or custom string chosen by the user. The bank handle identifies the bank or payment app.
One person can have multiple UPI IDs linked to the same or different bank accounts — for example, one via PhonePe and another via Google Pay. All UPI IDs belonging to the same account receive the same money; they are just different addresses for the same destination.
| Handle | Bank | App / Usage |
|---|---|---|
| @okicici | ICICI Bank | Google Pay / third-party |
| @ybl | Yes Bank | PhonePe |
| @paytm | Paytm Payments Bank | Paytm |
| @oksbi | State Bank of India | Google Pay (SBI) |
| @upi | NPCI / all banks | BHIM |
| @axl | Axis Bank | Axis Pay |
| @hdfcbank | HDFC Bank | HDFC MobileBanking |
| @okaxis | Axis Bank | Google Pay (Axis) |
| @ibl | IndusInd Bank | IndusInd |
| @kotak | Kotak Mahindra Bank | Kotak Pay |
The UPI QR Payload Format
A UPI QR code encodes a standard deep link using the upi://pay URI scheme. The payload is defined by the NPCI UPI Deep Link specification and is recognized by all UPI-compliant apps. Here is a complete example:
upi://pay?pa=merchant@okhdfc&pn=Raj%20Stores&am=150.00&cu=INR&tn=Invoice%20001
| Parameter | Example Value | Required | Description |
|---|---|---|---|
| pa | merchant@okhdfc | Required | Payee UPI ID (Virtual Payment Address) |
| pn | Raj Stores | Required | Payee name – URL-encoded, max 50 characters |
| am | 150.00 | Optional | Amount in INR – decimal with dot (omit for static QR) |
| cu | INR | Optional | Currency – always INR for UPI |
| tn | Invoice 001 | Optional | Transaction note / payment purpose – max 50 chars |
| mc | 5411 | Optional | Merchant Category Code (4-digit MCC) |
| tr | TXN001 | Optional | Transaction reference – for merchant reconciliation |
Static vs Dynamic QR Codes
There are two types of UPI QR codes. Choosing the right one depends on your use case: static for shops and recurring use, dynamic for precise invoice or checkout amounts.
| Feature | Static QR | Dynamic QR |
|---|---|---|
| Amount embedded | No – payer enters amount | Yes – fixed in QR code |
| Best for | Shops, general use | Invoices, e-commerce checkout |
| Reusability | Print once, use forever | New code per transaction |
| Payer input | Amount + PIN | PIN only |
| Reconciliation | Manual matching | Automatic via transaction ref |
UPI Apps Ecosystem
All UPI apps are fully interoperable — a payment from PhonePe lands instantly in an account linked to BHIM, Paytm or any banking app. There is no lock-in to any specific app or bank. As of 2025, market share by transaction volume:
Beyond consumer apps, every major Indian bank has its own UPI-enabled mobile banking app: SBI YONO, HDFC Mobile Banking, ICICI iMobile, Axis Pay, Kotak Pay and many more. All use the same underlying UPI infrastructure and accept QR codes from any source.
UPI's Global Expansion
UPI is no longer limited to India. NPCI International, a subsidiary of NPCI, has been extending UPI acceptance to countries with large Indian diaspora communities and strong trade ties with India. Cross-border UPI transactions link directly to partner payment networks in each country.
Singapore
PayNow
UAE
AECB / Mashreq
France
LYRA
UK
PayXpert
Bahrain
BFC
Mauritius
MCB
Nepal
NPI / Fonepay
Bhutan
BNBL
Malaysia
DuitNow (planned)
Thailand
PromptPay (planned)
In Singapore, Indian travellers can pay at merchants that display the PayNow QR code using their UPI app — the transaction is settled in SGD from the Indian bank account in INR. Similar corridors are active with UAE and Bahrain. The G20 mandate to interlink fast payment systems globally will further expand UPI's reach.
Security & Privacy
- 🔒PIN never in QR code: The UPI PIN is entered by the payer in their own banking app and is never encoded in the QR code or transmitted to the merchant.
- ✅Payment always authorized by payer: No charge can occur without the payer actively entering their PIN or biometric. QR codes are read-only payment requests.
- 🏦NPCI regulated, RBI supervised: UPI operates under the Payment and Settlement Systems Act, 2007. All transactions are logged and audited by NPCI.
- ⚡Instant refunds for failures: Failed or disputed transactions trigger automatic refunds within 24–48 hours per RBI circular.
- 🛡️Safe to share QR publicly: A UPI QR contains only your UPI ID and name – no bank account details, no IFSC, no sensitive data.
- 🌐Client-side generation: QRPayHub generates UPI QR codes entirely in your browser. No payment data is sent to our servers.