Behind the scenes when you use Google Pay to make a UPI payment at a store or online:

Scenario: Paying ₹500 at a store using Google Pay

1. 🧍♂️ Customer Action

You open Google Pay, scan the store's QR code, enter ₹500, and hit “Pay”.

2. 📱 Google Pay (TPAP) Initiates the Transaction

• Google Pay is a TPAP (Third-Party App Provider).
• It gathers:
• Your virtual UPI ID (e.g., you@okaxis)
• Store’s UPI ID (e.g., store@icici)
• Amount, remarks, etc.
• Google Pay sends this data to your linked PSP bank (say, Axis Bank).

3. 🏦 Your PSP Bank (Axis Bank) Verifies

• Axis Bank checks:

• Is your UPI account valid?
• Do you have enough balance?
• Is the UPI PIN valid (which you entered)?
• If everything checks out, Axis Bank says ✅.

4. 🔄 Transaction Sent to NPCI

• Now Axis Bank forwards the transaction to NPCI (National Payments Corporation of India).
• NPCI acts as the central switch/router for all UPI traffic.

5. 🏦 NPCI Sends to Receiver’s PSP (ICICI)

• NPCI routes the payment to ICICI Bank (store’s PSP).
• ICICI checks the store’s UPI ID and credits ₹500 to their account.

6. ✅ Confirmation Sent Back

• ICICI sends a success response to NPCI.
• NPCI notifies Axis Bank (your PSP).
• Axis notifies Google Pay.
• Google Pay shows "Payment successful" on your phone.

7. 📲 Both Parties Get Notifications

• You get a payment confirmation.
• The shopkeeper gets a credit alert.

🔐 Security Notes:

• The entire process happens in real time (within seconds).
• UPI PIN is encrypted and never stored.
• NPCI logs the transaction and ensures settlement between banks.

🛠 Tech Players Involved:

Role Who

TPAP Google Pay

Your PSP Bank Axis Bank (e.g.)

Merchant's PSP ICICI Bank (e.g.)

UPI Switch NPCI

Regulator RBI