Barcode not scanning at till: the four checks that fix it

Check four things in order: dark bars on a light background, a print size of at least 80%, bars that do not wrap around a curve, and whether the shop has added your number to its till list. If the scanner beeps but the screen shows no item, only the last check matters.

Why a barcode is not scanning at the till

When a barcode is not scanning at the till, the fault is almost always in one of four places. The print has too little contrast. The print is too small or cut too short. The pack curves the bars away from the scanner. Or the scanner reads the number fine, and the till has nothing to match it to.

Work through them in that order. The first three are about the label. The last one is about the shop's system.

The sound of the scanner tells you which half you are in. If it never beeps, the problem is the label, so start at check one. If it beeps and the screen says 'item not found', the label has done its job. Skip straight to check four.

For the tests you need the product, a ruler and a basic handheld USB scanner plugged into a laptop. A scanner like that costs around ₹1,500. When it reads a barcode, it types the number into any open text file. Use it rather than a phone. Phone apps are far more forgiving than a shop scanner, so a phone that reads your label proves less than you think.

Check 1: contrast

A till scanner shines red light at the label. It looks for the difference between dark bars and a light background. Anything that weakens that difference makes it struggle.

Black bars on white are the safe choice. Dark blue, dark green and dark brown bars also work on white. Red, orange, pink and yellow bars do not. Under red light they look the same as the white around them, so the scanner sees a blank space.

The background matters as much as the bars. Kraft paper, gold or silver foil, clear film over a coloured product and dark packs all lower the contrast. The fix is a plain white box under the barcode, either printed into the artwork or as a white sticker.

That white box must include a clear margin on both sides of the bars. This is called the quiet zone. Keep at least 4 mm of empty space to the left of the bars and 3 mm to the right. A border line, a bit of text or the edge of the label inside that space will stop the read.

Thermal labels need their own note. Direct thermal labels use no ribbon. They darken with heat, so a label left in a hot van or a sunny shop window slowly turns grey. The bars then blur into the background. For stock that sits on a shelf for weeks, switch to thermal transfer labels with a wax or wax-resin ribbon. They cost a little more per roll and they do not fade the same way.

Gloss can cause trouble too. Shiny lamination or clear tape over the barcode throws the light back at the scanner. Use a matte finish over the barcode area, or leave it uncoated.

Check 2: size

The standard retail barcode is about 37 mm wide and 26 mm tall at full size. That includes the numbers printed under the bars. You can shrink it to 80% of that size or grow it up to 200%. Below 80%, the thinnest bars get too thin for many shop scanners.

Measure your printed label with a ruler. If the bars plus both quiet zones come to less than about 30 mm across, the barcode is too small. Print it again larger.

Three things shrink a barcode without anyone noticing.

1. The print dialog. 'Fit to page' or 'scale to fit' quietly resizes everything. Turn it off and print at actual size.
2. The artwork file. A designer drags the corner of the barcode to make it fit the layout. Ask them to set the size as a number, such as 100% or 90%, and never resize it by eye.
3. The height. Bars cut down to a thin strip to fit a small label read badly, even when the width is right. Keep the full height if you can. If you must trim, keep at least half of it.

Your printer plays a part as well. A 203 dpi label printer builds each thin bar from only two or three dots. Small rounding errors then make some bars fat and others thin. On a printer like that, print at 100% or larger. A 300 dpi printer handles smaller sizes, around 80% to 90%, much better.

Inkjet on plain paper has the opposite problem. The ink spreads, the bars grow fat and the white gaps between them close up. Use coated label stock, or print the barcode a little larger than you planned.

Check 3: curvature and placement

Flat boxes rarely fail this check. Bottles, jars, tubes and pouches often do.

On a round pack, the scanner needs to see the whole width of the barcode at once. If the bars run up and down on a narrow bottle, the left and right ends wrap around the curve and fall out of view. The scanner sees only the middle and gives up.

The fix is to turn the barcode on its side. The bars then run around the bottle, like the rungs of a ladder. The barcode now reads along the height of the bottle, which is straight. As a simple rule, use the sideways layout on anything narrower than a drinks can.

Placement causes the rest of the failures in this check. Keep the barcode off seams, folds and the crimped ends of tubes. Keep it at least 1 cm from the edge of a pouch, where the film bends. Avoid shrink sleeves at the shoulder of a bottle, where they wrinkle. If the label goes on by hand, stick it to a flat panel and keep it straight, because a crooked label over a curve fails twice.

Check 4: the lookup table

If the scanner beeps, the barcode has done its whole job. A barcode holds only a number. It does not carry the product name, the price or the stock count. The till takes that number and looks it up in the shop's own product list. If the number is not in the list, the screen shows 'item not found' or a blank line.

So the fix here is not a new label. The shop needs to add your product to its list. Give them a one-page product sheet. For each item, list the number under the barcode, the product name, the pack size, the MRP and how many come in a carton. Many shops add new items once a week, so send the sheet a few days before the first delivery, not with it.

If the till shows the wrong product, the same number is probably on two items. Each variant needs its own number. That means every size, flavour and colour. If one number sits on a 250 g pack and a 500 g pack, the till can only ever show one of them. Give the second pack its own number and relabel that stock.

If the till shows the right product with the wrong price, the number is fine. The shop has typed the price wrong, so ask them to correct it from your sheet.

Sometimes a shop or an online store asks for details you have not heard of. In that case, tell us where you sell and we will tell you what to send them. You can see our number packs on the PurchaseBarcode home page.

A ten-minute test before the full print run

Print one sheet at actual size. Stick a label on the real pack, not on flat paper. Scan it ten times with the handheld scanner, from different angles and about 10 cm away. It should read on the first pass every time. Then compare the number it types with the number printed under the bars. They must match.

If you use direct thermal labels, leave one labelled pack in a warm spot for a day and scan it again.

When all ten scans pass, print the run. Then take one finished pack to the shop after they have added it to their list, and ask them to scan it at the counter. One clean beep with the right name and MRP on the screen, and the job is done.