A personal budget in one evening: bank statement + AI

Most people don't have a budget not because they don't want one, but because they picture months of manually logging every purchase. Yet all the data already exists — your bank has been keeping it for years. All you have to do is export it and have it sorted. In a single evening you can build a complete picture of your money: how much comes in, where it goes out, and whether anything's left at the end of the month — or whether you're quietly eating into your savings.

A typical scenario

Klára is twenty-nine, freelances, and has a nagging feeling that “money just disappears.” About 48,000 Kč lands in her account each month, and by the end of the month there's a couple thousand crowns left — sometimes nothing. Where it goes, she doesn't know; she just has a vague sense that “a lot goes on food.”

One evening she exports the last twelve months of statements, has it processed, and within an hour has an answer that doesn't exactly please her but does help. Subscriptions: eleven separate charges totaling 1,340 Kč a month, and she hasn't used three of those services in the past six months. Food broke down into two line items — groceries at 4,900 Kč and delivery at 6,200 Kč — and delivery turned out to be a number she wasn't expecting. And most importantly: three months in a row she'd had negative cash flow without noticing, because there was always some money sitting in the account regardless. She canceled four subscriptions and put a cap on delivery. Not a diet — just visibility.

How to do it

1. Export your statement as a CSV. Any bank can do this: in online banking, find your transaction history, pick a period (a full year works fine), and export to CSV or XLSX. The file will contain the date, amount, counterparty, and a note — exactly what's needed.
2. Anonymize the statement before uploading it. Don't skip this. Delete account number columns and the names of any counterparties you'd rather not share (your employer, your doctor, an ex). Date, amount, and a rough description of the payment are all that's needed for the analysis. And use a paid AI account with contractual data protection, not a free chat — financial data is about as sensitive as personal information gets.
3. Have the transactions sorted into categories. Upload the file and specify categories that make sense for you: housing, food, transportation, subscriptions, health, entertainment, kids, one-off expenses. Explicitly say that for unclear charges, AI should list them separately as “uncategorized” instead of guessing — you can fill those in yourself in five minutes.
4. Have it build a monthly summary. You want three things: income, expenses broken down by category, and cash flow. Cash flow is the difference between what comes in during a month and what goes out. It isn't your account balance — and that's the whole point. You can have a healthy balance and still have negative cash flow, because you're living off money you saved earlier. Positive cash flow means the month paid for itself; negative means your savings are paying for you. Have both calculated for every month and look at the trend, not a single number.
5. Move the result into a permanent template. A one-off analysis is nice, but useless again in two months. Have it generate a spreadsheet structure in Google Sheets, formulas for totals and cash flow included, or a Notion database with categories and monthly views. A permanent home is what turns a one-time surprise into an actual tool.
6. Set up a ten-minute monthly routine. New statement, same prompt, add one line. That repetition is exactly how you catch trends — delivery spending climbing three months running, or a subscription that crept in that you never signed up for.

The best tools

• Claude — analyzes the CSV and produces an artifact with a chart showing month-by-month trends without you building a single formula; it can even handle “my ten biggest expenses last year.”
• Google Sheets — the best home for a permanent template; a pivot table will total your spending by category and month for you, see the tip on a pivot table in two minutes.
• Notion — if you want your budget alongside your other notes: a database with categories, filters, and a monthly-entry template (templates in Notion databases).
• Dedicated budgeting apps — can connect straight to your bank and categorize automatically; they make sense once you already know which categories you actually want to track.

What you get out of it

• A clear picture: for the first time you see the whole year together, not individual charges. That's the difference between “that was expensive” and “that costs 4,000 Kč a year.”
• Time: one evening instead of months of manual logging — then ten minutes a month.
• Money: forgotten subscriptions and duplicate services turn up in this exercise for almost everyone. It's often the fastest money you'll make all year.
• Peace of mind: negative cash flow spotted in August gets handled very differently than negative cash flow spotted in December, once the reserve has already run out.

Pro tip

Pull out a separate list of every recurring payment — the same amount to the same counterparty every month. That's the part of your budget nobody actively decides on; it just leaves the account on its own, without asking. Most people underestimate their recurring expenses by quite a lot. And hold to the rule that applies everywhere on this site: AI proposes, a human approves. Don't give any tool the power to change or cancel anything on your account — categorization can go to the machine, but canceling a subscription stays with you.