Setting up rules so categorisation matches how you think

Bica sorts your transactions on its own and gets most of them right. Rules are for the ones where "right" depends on something only you know — and they win, permanently.

By António Avelar · Updated 22 August 2026 · 4 min read

Bica categorises transactions as they arrive, and for most of them it is right. The interesting ones are where “right” is not a property of the transaction at all — it depends on something only you know.

The supermarket run that is really a gift. The petrol that is a business expense in your household and a personal one in mine. The transfer to your sister that is family support, not a transfer. No amount of cleverness settles these, because the answer is not in the data. That is what rules are for.

What a rule is

A rule is a set of conditions and a category. Anything matching every condition gets that category, from the moment it arrives, permanently.

The conditions you can combine:

Two properties matter more than the list. Rules beat Bica’s own guesses — always, with no threshold or tie-break. And rules never touch a category you set by hand; if you have already made a decision on a transaction, it stands.

Start from a transaction, not from the rules page

The quickest way to make a good rule is not to sit down and design one. Open a transaction that is filed wrong, and choose Always categorize like this. The rule arrives pre-filled from that transaction, and you widen or narrow it from there.

This matters because rules written from memory tend to be too broad. Written from an actual transaction, you can see what you are matching.

Before you save, Bica shows you which existing transactions the rule catches, and offers to recategorise them. Take the offer when you are fixing a long-standing mistake — otherwise the rule only applies going forward and last year stays wrong.

Merchant or description?

Prefer merchant when the merchant is recognised. It survives the statement line changing format, a different terminal, a different city.

Use description contains when the line never resolves cleanly — a payment processor, a marketplace that bills under a parent company, a bank’s own fee lines. Pick the most distinctive fragment, and prefer something that is not a number: terminal ids and reference numbers change, names do not.

Use starts with rather than contains for bank-generated prefixes, where the useful part is at the front and everything after it varies.

Order, and why a rule can appear to do nothing

Rules are checked oldest first, and the first one that matches wins. Later rules never see a transaction an earlier one already claimed.

This is the single thing that confuses people. You write a precise rule for “petrol station, over €80, business fuel”, and nothing happens — because a broad rule you wrote months ago already claims every petrol station for transport.

Bica tells you when this is happening: creating a rule that an earlier one already covers shows a warning naming the earlier rule and where it files those transactions. The fix is to narrow or delete the earlier rule, not to add a third.

The practical consequence: write the broad rules first and the exceptions after, only if the exceptions are genuinely narrower. If you find yourself with three overlapping rules for the same merchant, the honest fix is usually one rule and a category rename.

How many rules you should have

Fewer than you think. Somewhere between five and fifteen for most people.

Rules are for cases where the answer is stable and personal. If you are writing a rule for something that happens twice a year, categorise it by hand — a hand-set category is permanent too, and it does not accumulate into a rule list nobody understands in a year’s time.

Signs you have too many:

• Two rules whose names you cannot tell apart
• A rule that has categorised nothing (Bica shows the count for each one)
• Several rules that exist because your categories are wrong — the categories are the thing to fix

That last one is worth dwelling on. A rule is a patch on a decision. If you need six rules to separate professional from personal spending, what you actually need is a professional category. Fix the shape and most of the rules disappear.

A good starting set

If you want somewhere to begin, these four earn their place for almost everyone:

1. Your salary. Description contains your employer’s name → Income. Everything downstream depends on income being right.
2. The mortgage or rent. The payment leaves monthly under a description that never changes → Housing. This is the anchor for fixed versus variable.
3. Any transfer to your own savings. So it stops counting as spending. This is the most common distortion in any spending total.
4. The one merchant you always argue with. Everyone has one. Settle it once.