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Part 4 of 7 · Shelf price checker series ~5 min read

Which mismatch to fix first

The first full walk produced 582 exceptions, and a list of 582 exceptions is a list nobody finishes. The ranking decides what gets done before the doors open, what waits for the week’s label run, and what is really a question for head office rather than for the store.

Key takeaways

  • Direction before size. The customer charged more than the label comes first, at any amount.
  • A shelf with no readable price is next, because no price is displayed at all.
  • Unit price obligations depend on floor area, so they differ store by store.
  • An undercharge is lost margin, and sometimes it is the till that is wrong.
  • An overcharge has two fixes: change the label, or match the till to it until you do.

The ranking, one exception at a time

An exception ranked from before opening to a question for head officeA vertical chain inside an AWS account container, entered from a box on the left labelled An exception, from a label or a bay with no label. Charged more than shown, meaning the till is higher than the label, with a side exit reading yes: Before opening, relabel or set the till to match. Nothing to compare, meaning no label, an unreadable one, or a line not sold, with a side exit reading yes: Today's label run, to fit, replace or take it down. Unit price at fault, where this store must show one, with a side exit reading yes: This week's run, to reprint per kilogram, litre or item. Charged less than shown, meaning the label is higher than the till, with a side exit reading yes: To head office, because either the label or the price file is wrong. The final step is Closed by a photo, when the next read shows the shelf agreeing. A note says the order is the policy: a four pence overcharge leaves at the top, while a forty pence undercharge waits until the bottom and goes to head office rather than the shop floor.AWS ACCOUNTAn exceptionfrom a label, or abay with no labelCharged more than shown?the till is higherthan the labelBefore openingrelabel, or set thetill to matchyesNothing to compare?no label, unreadable,or a line not soldToday's label runfit, replace, ortake it downyesUnit price at fault?where this storemust show oneThis week's runreprint per kg,litre or itemyesCharged less than shown?the label is higherthan the tillTo head officewrong label, orwrong price fileyesClosed by a photothe next read showsthe shelf agreeingThe order is the policy. A 4p overcharge leaves at the top; a 40p undercharge waits until the bottom, and goes to head office rather than the shop floor.
Fig 1. Four questions in a fixed order, and one way to close. The order is where the business says which kind of wrong it minds most.
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Why direction matters more than amount

A label showing a lower price than the till charges is a misleading price. The Price Marking Order requires the selling price displayed to be the final price the customer pays. Trading Standards can prosecute a breach as a criminal offence, and under the Digital Markets, Competition and Consumers Act 2024 the civil route carries fines of up to £300,000 or 10 per cent of worldwide turnover, whichever is higher. None of that depends on the amount being large.

A label showing a higher price than the till breaches nothing. The customer pays less than they expected and nobody complains. It is still money: the 58 undercharges in the first walk covered lines selling about 1,640 units a week between them, at an average of 23p a unit, which is about £377 a week given away without anybody deciding to.

The overcharges were larger, 97 lines selling about 2,210 units a week at an average of 31p, or about £685 a week. That is not why they go first. They go first because each one is a customer who read a price, believed it and paid a different one.

The second question catches exceptions with no difference to measure at all: a product on the shelf with no label above it, a label too worn to read, or a label for a line the till no longer sells. The first two mean no price is displayed; the third is clutter that sits where a real label should be. None of them needs a decision, only a label.

What the first walk found

Exceptions from one full walk grouped by kind and causeFour stacked vertical bars showing the exceptions from one full walk of the largest store. Overcharges total ninety-seven: forty-four where a promotion ended and its label stayed up, thirty-one where the price changed and the label did not, and twenty-two labels under the wrong product. Undercharges total fifty-eight: forty-seven where the price changed and the label did not, and eleven labels under the wrong product. Unit price faults total one hundred and forty-three. Nothing to compare totals two hundred and eighty-four: one hundred and twenty-nine products with no label, ninety-one labels too worn to read, and sixty-four labels for lines not sold. A note says the two left bars have a customer on the other side of them, while the two right bars are bigger and neither needs anybody to decide anything.0100200300400~97Overcharges~58Undercharges~143Unit prices~284Nothing to comparePromotion ended, label still upPrice changed, label did notLabel under the wrong productUnit price missing, wrong or per 100gNo label where the product isLabel too worn to readLabel for a line not soldThe two left bars have a customer on the other side of them. The two right bars are bigger, and neither needs anybody to decide anything.
Fig 2. The 582 exceptions from the first full walk, by kind and cause. Size and urgency run in opposite directions.

Unit prices are a per-store obligation

A shop with a relevant floor area of 280 square metres or less, counting the selling floor but not the stockroom, is exempt from showing unit prices on goods pre-packaged in constant quantities. It still has to unit price goods sold loose. Two of the chain’s five stores are above that line and three are below it, so the same label with no unit price is a fault in one building and acceptable in the next.

The checker therefore holds floor area as store data, with the date it was measured, and asks the unit price question per store. In the largest store the first walk found 143 unit price faults: 71 labels with no unit price at all, 52 still showing a price per 100 grams from a template older than the April 2026 move to per kilogram and per litre, and 20 where the unit price did not agree with the selling price and the pack size.

Fix the label, or fix the till

An overcharge has two fixes and they are not equivalent. Replacing the label makes the shelf agree with the till from then on. Setting the till to the label price until the label is replaced honours what customers have already been told, and it is the only fix that works before the label printer does. The checker offers both and records which was chosen, because the choice is a pricing decision and belongs to a person.

An undercharge is sometimes the till being wrong. A price cut keyed to the wrong line leaves the right line too dear at the till and its correct label looking high. So undercharges go to whoever owns the price file with a question attached, not to the store with an instruction to reprint.

What an exception holds

  • Kind. overcharge | undercharge | unit_price | no_label | unreadable | not_ranged.
  • Cause. promotion_ended | price_changed | wrong_position | absent | per_100g | arithmetic.
  • Difference. Pence per unit, signed, and the week’s units behind it.
  • Rank. From kind first and amount second, never the reverse.
  • Fix. relabel | till_matched | price_file_corrected, and who chose it.
  • Closed by. The photo that showed the shelf agreeing, not a tick.

The next post is what keeps the list short after the first walk: how long labels actually lag the till, and a swap list a store can work through in one pass.

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