How to categorize expenses without building a folder tree

The test every category should pass

A category earns its place if seeing its total at month end could plausibly change something you do. That is the whole test.

"Dining out — $420" passes: you might cook more, or decide $420 is fine and stop worrying. "Bank fees — $3" fails: there is no version of you that acts differently on that number, so it can live in Other.

Run that test on your list and it usually shrinks by a third. What remains is the set of numbers you will actually read.

Why flat beats hierarchical

Nested categories look tidy in a settings screen and cost you every single time you log a spend. Instead of picking a label, you navigate a tree — and at the leaf you face a judgement call that has no correct answer.

The deeper problem is that hierarchy encourages precision you will never use. If you split Groceries into Produce, Pantry, Meat, and Household, you now have four numbers where you had one, none of which changes what you buy.

expenie uses a flat, user-defined category list shared by expenses and income, with no hierarchy in v1. That is a deliberate constraint rather than a missing feature — it keeps logging to one tap and keeps budgets legible.

If you genuinely need a sub-split, a naming convention gives you most of the benefit with none of the cost: Business · Software sorts next to Business · Travel without becoming a tree.

A starting list that works for most people

Start here, then adjust after one honest month. Do not design the perfect list up front — you do not yet know your own pattern.

• Rent or mortgage — usually one large fixed line worth seeing alone.
• Utilities — power, water, gas, internet, phone.
• Groceries — food you cook at home.
• Dining out — restaurants, cafes, delivery, takeaway.
• Transport — fuel, transit, rideshare, parking, servicing.
• Health — insurance premiums, pharmacy, appointments.
• Subscriptions — recurring digital and membership costs.
• Shopping — clothes, household goods, electronics.
• Entertainment — events, hobbies, travel for fun.
• Debt payments — anything servicing a loan or card balance.
• Gifts and giving — presents, donations, family support.
• Other — the honest bucket for genuinely miscellaneous things.

Twelve labels. Most people need somewhere between ten and twenty. Below ten, the totals stop telling you anything specific. Above twenty-five, logging starts to feel like filing.

Handling the awkward cases

Three situations break every neat category scheme, and each has a pragmatic answer.

The mixed basket. A single supermarket trip with food, cleaning supplies, and a T-shirt. Assign the whole line to the dominant category and move on. Splitting a $90 trip into three lines costs you two minutes and buys you nothing you will act on. Only split when one component is genuinely large — a $600 appliance inside a grocery run deserves its own line.

The ambiguous merchant. Amazon, Costco, a corner shop that sells everything. Categorise by what you bought, not by where you bought it. If you truly cannot recall, Other is a legitimate answer and better than a fabricated one.

The genuinely one-off. A wedding, a house move, a medical event. Give it a temporary category for the months it runs, then retire the category. A one-off buried inside Shopping quietly ruins your read on normal months.

Transfers are not a category

This is the single most common mistake in a manual ledger. Moving money from checking to savings, or paying a credit card bill from your current account, is not a spend — it is a transfer between accounts you own.

Log those as transfers, not expenses. If you categorise them, your monthly spend inflates by the exact amount you moved, and "Savings" appears as your biggest expense category, which is nonsense.

expenie treats transfers as their own transaction kind, and they are deliberately not categorised. Paying a credit card bill is a transfer onto the card that reduces the amount owed — it is not a new expense, because the expense was recorded when you used the card.

Keeping the list clean over time

Category lists rot in a predictable way: near-duplicates appear, one-offs never get retired, and a long tail of single-use labels accumulates.

Every few months, do a short pass:

1. Merge near-duplicates. Food and Groceries doing the same job splits your budget spend across two limits and hides overspend.
2. Retire finished one-offs so they stop cluttering the picker.
3. Fold anything with one or two transactions all year into Other.
4. Check that every category you kept still passes the decision test.

expenie dedupes categories case-insensitively when you create one inline, with a unique index enforcing it, specifically because duplicates silently split budget spend. That still leaves genuine near-duplicates like Food and Groceries for you to merge by hand.

How categories drive budgets

Categories are not filing for its own sake — they exist so a budget has something to limit. In expenie, a budget is one category, one calendar month, and one limit, and spent is the sum of expenses in that category that month.

That is why category design comes first. A limit on Groceries is actionable. A limit on Food › Groceries › Produce is arithmetic homework. Size your list to the decisions you make, and the budget layer takes care of itself.