"I spend a fortune on groceries" is the sentence, and it almost never comes with a breakdown. We know the total because the bank tells us, and that's where it stops. This guide is the method for getting from a total to something you can decide with: which categories take your money, which specific products went up, how much is price and how much is you.
A total isn't information
A total blends three separate things that move independently: how much you buy, at what price, and where. If you spent £60 more this month, that could be a price rise, a dinner party, or a trip to a pricier shop. While they're added together you can't act, because each one is fixed differently — and one of them doesn't need fixing at all.
That's why banking apps don't solve this: they tell you "Groceries: £412". It's the number you already had, with a pie chart around it.
Step 1: get from the total down to the lines
Everything starts with an itemised receipt — product by product, with prices. It's the only level at which the three things above come apart. Without lines there's no analysis possible: with a bank charge, all you can do is have feelings.
Step 2: group by category, but don't stop there
Grouping into fresh food, cupboard, drinks, cleaning and toiletries does one useful job: it shows you at a glance which block eats your money, which is often not the one you expected. It's a good first map.
But a category isn't actionable either — you can't "reduce cupboard". It's the intermediate step that tells you where to look closely.
Step 3: sort by impact in money, not by percentage
This is where nearly everyone ends up with the wrong list. The product that rose most in percentage terms is almost never the one costing you most. What matters is rise × how often you buy it.
Example (invented figures to illustrate the method, not market data):
| Product | Rise | Times a month | Real impact |
|---|---|---|---|
| Speciality spices | +40% | 0.2 | +£0.30/month |
| Ground coffee | +8% | 4 | +£3.80/month |
The headline is the 40%. The money is in the 8%. A list sorted by real monthly impact usually has five or six products on it, and those five or six explain most of what changed in your spending.
Step 4: separate what's up to you from what isn't
With the short list in front of you, each product falls into one of four buckets:
- It's price, and it's cheaper elsewhere. The easy case: same branded product, different chain. Requires giving up nothing.
- It's price, and it's the same everywhere. Here the decision is about size, an alternative brand, or quantity. Or accepting it knowingly, which is also a decision.
- It's a size change in disguise. The price didn't move but the contents did. Only visible in price per kilo or litre.
- It's you. You buy more, or you buy and it gets thrown away. That isn't inflation and changing supermarket won't fix it.
That split is the whole point of the exercise. You don't need to act on all four buckets; you need to know which one every pound is in, because deciding without knowing is guessing.
Step 5: check whether the decision worked
Switching brand or shop is only a good move if it shows up next month. With the lines saved, checking is direct: same product, same month last time, what did you pay now? Without that loop you aren't controlling your spending, you're trying things.
How not to give up in week two
All of the above can be done with a spreadsheet, and that is exactly what almost nobody sustains. The obstacle isn't any single step: it's typing every line of every receipt and, above all, deciding each time whether "WHL MILK 6X1L" and "Whole milk 6-pack" are the same product. That reconciliation work is what kills the habit.
It's the part Grotally does for you: you photograph the receipt, the app extracts the lines, works out when two spellings are the same product, normalises to price per unit of measurement and compares — over time and across the shops you actually use. You're left with the part that can't be automated, which is deciding.
If you'd rather have the background on why your figure doesn't match the official one first, it's in why your shop rises faster than the CPI.