Why is there a QR code on the bill?
The QR code carries a web address that leads to the summary of the transaction. The customer scans it and reads online what the merchant transmitted; on an electronic bill, a “view the transaction online” link sits under the code. It is the verification point offered to the consumer, and the only part of the bill they can check for themselves.
Half-faded text is still readable to the human eye. A QR code is read by a device instead: its error correction compensates for partial damage, but beyond a certain point the code can no longer be read at all. Print quality therefore decides whether the customer will be able to look up their transaction.
What degrades a QR code at print time?
There are four causes, and none of them is a printer defect. Poor or aged thermal paper darkens unevenly. A dirty print head leaves white bands running in the paper-feed direction. A roll narrower than the setting shifts and clips the code, and ambient heat greys the background, which reduces the contrast that decoding depends on.
| Cause | Symptom | Fix |
|---|---|---|
| Inconsistent paper quality | Grey print, weak contrast | Change the batch and check the client’s supplier |
| Dirty print head | Vertical white bands across the code | Clean the head, then reprint |
| Wrong roll width | Code shifted or clipped on one edge | Align the paper guide with the driver setting |
| Heat or light | Greying background, stock darkening in storage | Move the stock and the printer away from heat sources |
What paper and maintenance should you plan for?
The roll width must always match the printer setting. At the counter the common format is 80 mm, which is the format of the MG80 in the G4POS catalogue. Thermal paper darkens through contact with a heated head, so it ages with heat and light, even before anyone prints on it. Stock stored above an oven is already damaged on installation day.
- Confirm the accepted width and note it in the client file, since it is also a consumable to reorder.
- Store rolls away from heat, direct light and cleaning solvents.
- Clean the print head on a schedule agreed with the client.
- Keep a fresh roll on hand to tell a paper problem from a printer problem.
How do you test the scan before leaving the site?
The only reliable test is to scan the code. Use a phone, since that is the customer’s tool, then a 2D reader if the business owns one: the SC310 in the catalogue reads 1D and 2D symbologies. A code that a phone decodes on the first try, at normal distance and under the counter lighting, will stay readable for the customer.
- Print a real bill from the client’s SRS, on the delivered station.
- Scan the code with a phone, at the distance a customer would use.
- Repeat on a receipt printed after five minutes of activity, with a warm head.
- Record the result in the file so you can show it if the question comes up later.
Can the client use electronic bills only?
The bill may be handed over on paper, sent electronically (by email or text message) or both at once. A consumer can still require a paper bill, unless the terms of use they agreed to beforehand provide for electronic delivery only. A “paperless” establishment must therefore still be able to print.
Even when a client says they will never print, include a printer and state it in the quote. A printer ordered afterwards, in a hurry, generally costs more than one planned from the start.