A receipt from Mercearia Bico, 11 Jan 2026, EUR 41.20, has fourteen lines on it. Twelve are food. One is a phone cable at EUR 9.99 and one is a birthday card at EUR 2.50. That is one merchant, one piece of paper, and at least three honest answers to the question of what it was. Every difficult decision in Slip’s categories comes out of that receipt.
The category lives on the receipt
Classifying each line is more accurate and much worse to use, because it turns one decision into fourteen. In testing, reviewing a supermarket receipt line by line took a median of 74 seconds against 4 seconds for putting a single category on the whole thing. So the category sits on the receipt, and splitting one is two taps for the people who want it. Splitting is used on 6% of receipts, nearly all of them supermarkets and pharmacies, which is why it stays off the main path.
“Other” is a hole in the floor
The first release had 41 categories and an “Other” bucket. Within two months, 22% of all receipts were sitting in “Other” and staying there. We renamed it “Unsorted”, moved it to the top of the list with a count beside it, and wrote one plain line underneath: nothing here has a category yet. It fell to 4% in six weeks, because people finish what looks unfinished and leave alone what looks done. The 41 categories became 17 in the same release.
A pharmacy is not the same category for two people
Farmácia Estrela is Health for one person, Household for someone who buys shampoo and sunscreen there, and Business for a physiotherapist buying tape. No single answer is right for all three, so corrections are personal. After three corrections on the same merchant, Slip stops guessing and uses your answer, and that preference stays on your account instead of being pooled into anyone else’s. The median account makes 11 corrections in the first month and about 2 a month by day 60.
What we cannot fix
There is no correct taxonomy, only the one that matches how a household already thinks about money. Categories can be renamed and new ones added up to 24, because a list longer than a screen stops being a list and becomes a search problem. Slip has no way of knowing that the EUR 9.99 cable was bought for work, and it will not ask, because asking about every line is the thing we deleted in the first place. If it matters, the split is two taps away. If it does not, the receipt is filed and the day carries on.