Crime PayPay sound fraud exposed

How is this even possible? Wouldn't the business owner receive an instant notification from PayPay?

A woman was charged with fraud after allegedly obtaining goods from several businesses by falsely claiming to have completed cashless payments. Prosecutors say she selected items, produced a sound on her smartphone indicating a successful PayPay transaction, and left the premises without paying. The scheme came to light only after merchants later reviewed their records. The defendant admitted to the charges during proceedings at the Nagasaki District Court.

The PayPay app has a setting to adjust the volume of its payment sound. When the volume selection is chosen, the app automatically emits that sound. The woman played the sound through this way to mislead shops into believing that she had actually completed purchases of items through the app. Prosecutors said around January to February in 2025, the woman heard from a person who avoided paying a bill using the PayPay sound. She had become acquainted with the bill cheater at her previous workplace, a restaurant. The woman searched the internet to learn such methods. According to investigators, the woman committed similar offenses at other hair salons and restaurants. She reached settlements with the victims in those cases.

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The answer to my initial question is in the article:

The shopowner said he had trusted PayPay users and hesitated to ask customers to show their smartphone screens because he felt it was disrespectful. At other shops apparently victimized by the woman, investigators said staff members expressed discomfort about asking customers to show their smartphone screens to confirm payment, saying it felt "awkward" or "impolite." A senior investigator said a customer‑service culture based on mutual trust between shops and customers overlapped, allowing the woman to easily use the sound method.

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The PayPay app has around 70 million users and accounts for roughly 70% of Japan's QR-code payment market.