The supermarket receipt line most shoppers ignore – and how it reveals sneaky price hikes

By the time you reach the car park, the receipt is already half‑crumpled in your hand. You scan the total, wince a little, maybe circle a couple of big-ticket items in your head, then shove the slip into a bag or the bin.

You did the same shop as last month. Same pasta, same cheese, same washing‑up liquid. Yet somehow the total looks fatter. You blame “inflation” in general and move on. But the clue to what has really changed is printed in tiny type in a place most people barely glance at.

The line isn’t the total. It isn’t the list of products. It’s the unit price.

The quiet line that tells you when you’re being squeezed

Every receipt in a UK supermarket carries two prices for most items: what you paid, and what that works out to per kilo, per litre, or per 100 g/ml. That second one, the unit price, is where the truth lives.

On the shelf, the unit price is meant to help you compare brands and sizes. On the receipt, it becomes a time machine. Compare it to a previous shop, and you can see which products have crept up, even when the pack size has quietly shrunk or a “promotion” muddies the water.

Supermarkets know most people never bother. They look at the bold number, not the smaller one next to it.

If you only ever check the big total, you feel poorer but never quite see who made you poorer.

Unit prices expose the tricks: slight changes in weight, oddly sized “value packs”, and loyalty‑card “deals” that aren’t deals at all. The number is small, but the pattern is not.

Shrinkflation, stealth rises and the illusion of a bargain

The classic move is shrinkflation. Your usual cereal goes from 500 g to 450 g, but the price label on the shelf barely budges. On your receipt, the price looks “unchanged”. Your cupboard looks the same. Only the unit price tells you you’re paying more for less.

Another favourite is awkward pack sizes. Multi‑buy offers on crisps or yoghurts come in slightly smaller individual packs. The big “£££ OFF” flash on the front distracts you from the reality that the per‑100 g cost is higher than the old, simple pack. Again, the receipt’s unit line quietly calls it out.

Loyalty‑card prices add another layer. You might see:

• Standard price
• Club price
• Supposed “was/now” discount

On paper, it feels like a bargain. On the receipt, the unit price can show that your “exclusive” deal is still more expensive than last month’s regular price.

Over a month’s shopping, that gap can run to tens of pounds, even if you never pick up anything that looks obviously luxury.

How to read the unit line without needing a spreadsheet

You don’t need to become a walking calculator. You just need a simple habit and one or two reference points.

Next time you shop, pick three or four staples you always buy:

• Your regular loaf of bread
• Milk
• A basic pasta or rice
• A cleaning staple (washing‑up liquid, laundry detergent)

Glance down your receipt and note the unit price next to those items. You don’t even have to write it down; a quick photo on your phone will do. Then, on your next trip, check those same lines. Has the per‑kilo or per‑litre number shifted?

If it has, you’ve learned something very specific: not “everything is up”, but “this brand/size has moved”.

From there, you can react:

• Swap to a different size of the same product if the unit price is lower.
• Test a supermarket own‑brand if the unit price difference is big.
• Ignore flashy offers if the unit price doesn’t justify them.

It’s a tiny ritual that takes less than a minute, but it gives you back a sense of control.

The three patterns that reveal a sneaky price hike

Once you start looking, the same patterns repeat.

1. Same price, smaller pack

The till shows £2.50, just like last month. The pack in your hand is now 400 g instead of 450 g. The label might say “new recipe” or “new look”. The unit price jumps; the front‑of‑pack price doesn’t.

On the receipt, it reads something like:

• £2.50 (£6.25/kg)

Last month, the same line might have been:

• £2.50 (£5.55/kg)

Same spend, less food. Only the unit number tells the story.

2. “Family size” that isn’t a saving

Bigger isn’t always cheaper per kilo. A “family” pack or “value” bottle can sometimes carry a higher unit price than two smaller packs, especially during a promotion on the smaller size.

Your receipt will show:

• £3.90 (£7.80/kg) – Family pack
• £2.00 (£6.67/kg) – Standard pack (on offer)

Most people see £3.90 vs £2.00 and assume the bigger one must be better value. The unit line quietly disagrees.

3. Loyalty deals that move the baseline

A loyalty discount can mask a new, higher normal price. The shelf might show:

• Was £3.00, now £2.40 with card

You feel you’ve “saved 60p”. But if your old receipts show that same item at £2.20 a few months ago, your so‑called saving is actually paying 20p more than before. The unit price confirms it.

Over time, your receipt history becomes a private archive of how your supermarket nudges those baselines up.

A quick receipt routine that actually saves money

Turning the unit line into a habit doesn’t require becoming a budgeting monk. Treat it like checking your phone battery before leaving the house: a light, automatic scan.

Try this routine for your next few shops:

1. At the till, keep the receipt instead of declining it.
2. On the way out or in the car, find three staple items and check the unit prices.
3. Take a photo of the receipt if you’re likely to throw it away.
4. At home, spend 60 seconds comparing this shop’s photo with the last one.

You’re not trying to track everything. You’re just waiting for any one staple’s unit price to jump or a pack size to shrink. When something moves, adjust:

• Downgrade one brand for that week.
• Swap a convenience size for a better‑value size.
• Decide if a loyalty scheme is genuinely helping or just hiding rises.

Over a year, these small, informed swaps add up more than you’d expect.

Why supermarkets hope you never look too closely

Supermarkets aren’t villainous masterminds, but they are under relentless pressure to protect margins while keeping you feeling comfortable. Adjusting pack sizes, leaning on promotions, and steering people into loyalty schemes are all part of that game.

The assumption behind much of it is simple: shoppers don’t check the fine print. They buy on habit and feeling, not on per‑kilo arithmetic.

Once you start reading that little line, you partially step outside the game. You’re no longer reacting only to headline prices or colourful offers. You’re watching the underlying cost of what actually feeds and cleans your household.

That doesn’t make inflation disappear. It just means you can see where it’s hitting hardest, and where you still have room to manoeuvre.

What to watch	Where it shows	Why it matters
Unit price (per kg/l/100 g)	Next to each line on your receipt	Reveals real cost and shrinkflation
Pack size changes	Product label vs old receipt	Shows when “same price” hides less product
Loyalty “savings”	Discounted line on receipt	Tells you if the deal beats past normal prices

FAQ:

• Do all UK supermarkets show unit prices on receipts? Most large chains do for grocery staples, but the format can vary. If you can’t see it clearly, the shelf label will still show the unit price for comparison.
• Is it really worth checking for just a few pence difference? Individual gaps can look tiny, but across dozens of items and a year’s shopping, they can add up to hundreds of pounds.
• What if I mostly buy own‑brand already? Own‑brand lines also shrink and creep up in price. Unit prices help you spot when an own‑brand has quietly stopped being the bargain it once was.
• Can apps replace keeping paper receipts? Yes. Many banking and supermarket apps store itemised receipts. You can still compare unit prices over time by taking screenshots.
• Is complaining to the supermarket about shrinkflation useful? You can’t force prices down, but feedback does get noticed, particularly when many customers flag the same product. It can also push clearer labelling and fairer promotions.

The next time your total makes your eyebrows rise, don’t just sigh at “the cost of living”. Run your eyes one line lower. That quiet little number is telling you exactly where your money is really going.