How do I know which UPI PIN to enter?

After entering the amount and proceeding with the payment, you will be directed to the UPI PIN page of the bank you've selected for the transaction. If you've already set up your UPI PIN for this bank through any UPI app, you can use the same PIN here. If you haven't set up a UPI PIN yet, you will be taken through the PIN setup process during registration. Alternatively, you can visit the UPI settings screen to set up your PIN for the selected bank.