What is in this guide
A price book is a short written record of what you actually pay for the items your household buys again and again, kept over several shopping trips so you can tell a genuine price change from normal variation. It takes about ten minutes to set up and a minute or two to update each shop.
Why ten items, not everything
Trying to track every grocery item burns out fast and nobody keeps it up. Ten items is manageable and covers most of the value, because the things a household buys most often are usually the things worth knowing the real price of.
Pick items you buy at least monthly: bread, milk, a cereal, toilet paper, laundry powder, a protein your household eats weekly, pet food if you have a pet, and whatever else repeats on your list. Unit pricing on household basics is a good place to start if you are not sure which pack size to track, since it covers comparing pack sizes on items like toilet paper and cleaning products directly.
Step 1: Set up the record
Use a notebook, a phone note or a simple spreadsheet, whichever you will actually open again. For each of the ten items, record the exact product, the pack size, the seller and the price, with the date of each entry.
| Field | What to put in it |
|---|---|
| Item | The product name and variant you actually buy |
| Pack size | The quantity or weight on the label |
| Unit price | Price per 100g, per litre or per item, if shown |
| Seller | Where you bought it, or where you saw the price |
| Price paid | What it cost that trip |
| Date | The day you recorded it |
Recording the unit price alongside the shelf price matters because pack sizes change and a “bigger” pack is not always cheaper per unit. How unit pricing works at the supermarket explains how to read the unit price tag and why it is the number worth comparing, not the price on the front of the pack.
Step 2: Record every trip, not just the specials
The book is only useful if it has normal-price entries in it, not just discounted ones. If you only write something down when it is on special, you have no baseline to compare against and every entry will look like a saving.
Update the book each time you buy one of the ten items, even when the price has not moved. A flat line across several trips is useful information: it tells you the normal price, so the next advertised discount can be checked against something real.
Step 3: Read the book before a big shop
Before stocking up on a special, check the item against your own recorded prices rather than the shelf ticket’s comparison price. If today’s price matches what you have paid several times before, it is an available price, not a new saving. If it is genuinely lower than your recorded range, that is useful evidence for buying extra.
This is the same comparison principle behind unit pricing generally: a standard unit of measurement lets you compare prices and find the best value for money, which is the stated purpose of the ACCC’s Unit Pricing Code for supermarkets and grocery retailers [S1]. A price book applies that same comparison across your own shopping trips over time, rather than only between products on the shelf on one day.
If you want to judge a single advertised sale in more depth, including what counts as weak evidence and when to walk away, the longer method for checking whether a sale is real covers that decision on a single planned purchase. If the bigger goal is finding where the whole grocery bill is going, a full receipt audit looks at the trolley as a whole rather than ten repeat items.
Step 4: Keep it current
Review your ten items every few months. Drop anything the household has stopped buying and add whatever has become a new regular. A price book that lists discontinued products is not giving you a useful comparison.
Keep old entries rather than overwriting them. A short history across a few months is what makes the book useful; a single price with nothing to compare it to is just a receipt.
Start with the first item on your list. Write down today’s product, pack size and price, and do the same at your next shop.
How we checked this: Checked on 2 October 2026 against the ACCC’s Unit Pricing Code guidance. The item-selection and record-keeping method is an editorial suggestion, not a tested savings programme. No retail prices were sampled and no savings total is claimed.
The one-page family week
One printable page that holds the whole week: meals, school, activities and who is doing the pickup. Free, and we send one useful email a week.
One email a week. No spam, unsubscribe in a click.
