Tags, and how they differ from categories

Every product with categories eventually adds tags, and everybody asks the same question: what are these for that categories are not?

A transaction has one category and any number of tags

That is the whole difference, and everything else follows from it.

A category answers "what kind of spending is this?" — groceries, dining, transport. It is exclusive because a budget has to add up: if a transaction could be in two categories, no budget figure would mean anything.

A tag answers any other question you want to ask later. Holiday in Spain. Reimbursable. Kitchen renovation. Tax deductible. None of those are kinds of spending — a holiday is groceries and dining and transport, all at once — so none of them can be categories without breaking the thing categories are for.

When a tag is the right answer

A project or an event. The renovation, the wedding, the trip. It cuts across categories by definition, and you want the total.

A state rather than a kind. Reimbursable, disputed, check this. Something that will stop being true, which a category never should.

A person or a purpose, where a household shares accounts and you want to see one thread of it.

When it is not

If you find yourself tagging every transaction from one merchant with the same tag, you probably wanted a category — or a rule to set one. Tags are for cross-sections; categories are for kinds.

Using them

Add tags on a transaction, or select several and tag them together. Then filter the transactions page by a tag to see the whole thread and what it came to.

Tags are the household's, not yours alone — so a tag one person adds is one everybody can see and use, which is what makes them useful for a shared project and worth naming clearly.