There's a particular kind of Sunday afternoon where you sit down and build the perfect category list. Groceries, but also Household. Coffee, separate from Eating Out. Transport, split into Fuel and Public Transport and the occasional taxi. By the end you've got twenty-two expense categories for budgeting, it looks like a real system, and you feel briefly excellent about yourself.
Six weeks later you're staring at a receipt from a corner shop with bread, batteries and a bottle of wine on it, and you have no idea which of your twenty-two boxes it goes in. So you put it in Other. Then you do that again on Thursday. Then you stop opening the app. The categories weren't wrong exactly, they were just built for someone who doesn't exist: a version of you with more patience than you have on a Tuesday.
Why most expense categories for budgeting quietly collapse
The mistake is copying an accountant. Accountants categorise to describe the past accurately, and accuracy is their whole job. You're doing something different. You're categorising so that future-you can look at a number and change behaviour. Those two goals want very different lists.
A descriptive list wants precision, so it grows. Every time you hit an edge case you add a category, and the list gets longer while the useful information gets thinner. Spread ninety transactions across twenty-two buckets and most buckets hold three or four things. Three or four things is noise. You can't see a trend in it, and you can't tell whether last month was better than the one before.
The second failure is subtler. Long lists make logging slow, and slow logging makes you skip entries. The cost of a category isn't just the mental effort of choosing it, it's every future purchase you don't bother recording because choosing felt like work.
The only test a category needs to pass
Here's the rule I'd defend in an argument: a category earns its place if seeing its monthly total would make you do something differently. That's it. If the answer is no, it's admin, and admin is what you quit.
Run the test honestly. Knowing you spent $340 on groceries might make you plan meals or shop somewhere cheaper, so Groceries survives. Knowing you spent $11 on stamps and envelopes changes nothing at all, so Stationery does not survive.
If a category's total wouldn't change a single decision you make next month, you're not budgeting with it. You're filing.
Should coffee be separate from eating out? Only if you suspect coffee specifically is the leak and you'd act on the number. For most people it's one more decision at the till for no benefit.
How many expense categories should you actually use?
Somewhere between six and ten, and closer to six when you're starting. You can always split one later once you've got a couple of months of data telling you where the interesting mess is. Splitting a category that turned out to matter is easy. Merging fourteen dead ones is miserable, and by then you've usually already given up.
A starting set that works for most people:
- Fixed costs. Rent or mortgage, bills, insurance, the phone contract. Anything you can't change this month without a phone call.
- Groceries. Food that comes home with you and gets eaten later.
- Eating out. Food someone else made. Coffee lives here unless you have a specific reason to pull it out.
- Transport. Getting places, however you do it.
- Fun. Nights out, hobbies, the impulse purchase you enjoyed. This is the one people are tempted to fragment. Don't.
- Everything else. Haircuts, a birthday present, the charger you had to replace. If this bucket gets suspiciously large, that's your signal to split something out of it.
Subscriptions are a reasonable seventh if you have a lot of them, mostly because the total is genuinely shocking the first time you see it.
What to do with the awkward ones
Every real budget hits four edge cases in the first fortnight, and how you handle them decides whether the system holds.
The mixed receipt. Bread, batteries and wine on one till slip. Don't split it into three entries. Put the whole thing where the bulk of the money went and move on. You lose a couple of dollars of accuracy and you save yourself the exact friction that kills the habit.
Credit card payments. These are not spending. The spending happened when you bought the thing, possibly weeks earlier. Logging the card payment as well double-counts it and makes your totals look deranged. Treat it as moving money between two places you already own.
Big one-offs. A flight, a new laptop, a deposit. Dropping a $900 purchase into a normal category wrecks the month and makes the comparison with last month meaningless. Keep them somewhere separate, even if it's just a note, so your regular categories still tell you something about regular life.
Money you fronted for other people. Paying for a group dinner isn't a $180 restaurant habit. Until people pay you back it's a loan, and it belongs in whatever system you use for shared costs rather than sitting in Eating Out and quietly ruining the number.
Give yourself one Other bucket and let it be genuinely messy. The instinct to eliminate Other is what grows the list back to twenty-two. A category you can't classify into in three seconds isn't rigorous, it's just slow.
How to know your categories are working
After a month, look at the list and ask two things. First, did any category surprise you? A budget that confirms what you already assumed isn't teaching you anything, and it usually means your categories are too broad to show the leak. Second, was there a category you never thought about again? That one's dead weight, so fold it into something else.
You want the list to be slightly uncomfortable. The categories worth keeping are the ones where you flinch a bit at the total, because flinching is the mechanism. Nothing about a tidy spreadsheet changes behaviour on its own. Noticing does.
And give it a couple of months before you rebuild anything. One month of data is a mood, not a pattern. Everyone has an expensive January.
Where Bud fits
Bud is built for people who log as they go rather than reading a report afterwards, which is why the categorising has to be fast or the whole thing falls apart. Adding an expense takes about seven seconds, and the Action Button on iPhone gets you to the entry screen without hunting for the app first. Buddy, the built-in AI assistant, handles the sorting and answers plain questions like where the money went last week, so you're not maintaining a taxonomy by hand while standing at a till.
There are no bank logins anywhere in Bud, so nothing arrives pre-categorised by a machine that has guessed wrong. That's a real trade: you do the entering, and in exchange the categories reflect how you actually think about your money instead of how a bank's transaction feed labels a merchant. Shared costs have their own place too, with bill splitting built in and Splitwise import if that's where your group already keeps score. It's free to download, with Bud Plus at $1.99 a month or $15.99 a year.
Start with six categories, keep them for two months, and only then split the one that's bothering you. Bud is on the App Store if you want somewhere to put them.
Track your money in seconds, not spreadsheets.
Bud is free to download, built for iPhone, and never asks for a bank login.
