Why Keep Your Own Price History From Grocery Receipts

Ask yourself what you paid for a litre of olive oil three months ago. Most people can give a rough answer, and most of those answers are wrong. Not wildly wrong, but wrong enough that you cannot tell whether the price you see today is a good one, a normal one or a new high.

That gap is the reason to keep your own price history. Not a market survey, not a list of every store’s prices, just a record of what you actually bought and what you actually paid.

Memory is not a price tracker

Prices drift in small steps. A pack of coffee goes from 7.49 to 7.79, then to 7.99, then a promotion takes it back to 7.29 for two weeks. Each step is small enough to feel like noise. After a year you remember “coffee got more expensive” but not by how much, not when, and not whether last week’s deal was a deal at all.

Memory also anchors on the wrong number. People tend to remember the last price they noticed, which is often a promotional price or a price from a different pack size. Comparing today’s shelf with that memory tells you very little.

The shelf only shows today

A shelf tag answers one question: what does this cost right now, here. It does not tell you:

• what you paid for the same product last month,
• whether the pack got smaller while the price stayed the same,
• what you paid after the discount at the till,
• how this product’s price moved compared with the rest of your basket.

Only a history answers those questions, and only a history built from your own purchases answers them for the things you actually buy.

Shelf price and paid price are different numbers

The price on the shelf is not always the price you pay. Multi-buy offers, campaign lines and discounts printed at the bottom of the receipt all change what a single item really cost you. If you buy two packs of pasta at 1.80 each and the receipt shows a 0.60 discount on the pair, each pack cost you 1.50, not 1.80.

A useful price history keeps both: the shelf unit price printed on the line, and the paid unit price once discounts are spread over the lines they belong to. We go into this in more detail in shelf price vs paid price.

Your receipts already hold the data

You do not need to write anything down in the aisle. Every receipt already lists the store, the date, each line, the quantity, the unit price, any discounts, the VAT and the total. The problem is that receipts end up in a pocket, a bag or the bin, and thermal paper fades.

Turning those receipts into data gives you a record you never had to type. A small example of what a few months of receipts for one product can show:

Month	Pack	Paid	Per kg
June	500 g	2.49	4.98
July	500 g	2.69	5.38
August	450 g	2.69	5.98
September	450 g	2.29 (promo)	5.09

Looking only at the price tag, July to August looks flat. Per kilogram, it went up by about 11 % because the pack shrank. That is exactly the kind of change memory misses. More on that in shrinkflation.

What a personal price history lets you do

Once you have a few weeks of receipts recorded, you can:

• Spot real deals. If the lowest price you ever paid for a product is 3.20, a “special” at 3.40 is not special.
• Notice creeping increases. Small steps add up. A history shows the first and last price and the change in percent.
• Compare pack sizes fairly. Unit price per kg, per litre or per piece puts a 750 ml bottle and a 1.5 l bottle on the same scale. See how to compare unit prices.
• See your own inflation. The official figure is an average over everyone. Your basket is yours. See personal inflation.
• Understand your spending. Monthly totals, categories and top products come from the same receipts.

Why not a spreadsheet?

You can do all of this by hand. Some people do, for a few weeks. The trouble is that a receipt with 30 lines takes a long time to type, the same product is printed with a different name at a different chain, and every discount line has to be divided over the right items. Most spreadsheets are abandoned long before they hold enough history to be useful.

How Tasarruf helps

Tasarruf turns receipt photos into this history for you. You scan a receipt, the app reads the store, date, lines, quantities, unit prices, discounts and total, checks that the numbers add up, and asks you to review only the fields that look wrong. The same product on different receipts becomes one product, with its first, last, lowest and highest price, a chart, and both shelf and paid unit price. Right after saving, a card shows which products went up or down. Start with Tasarruf.