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dagss • 01/03/2026 • 1 reply • view on HN

There's a difference between UI and code. In code, it is more complicated to do

    if (change.direction == OUT) {
        total -= change.value
    } else {
        total += change.value
    }
than to simply use negative numbers and do

    total += change
The same in accounting, it can in my experience often be convenient that your Entry database tables look like

    account          amount
    ---              ---
    income/sales     -100
    receivables      +100
rather than

    account       debit    credit
    ---           ---      ---
    income/sales           100
    receivables   100
The first one is just simpler, and you also get the nice graph properties (cuts, zero-sums, etc) discussed in the OP. Simpler database model, simpler code, less cases to test, easier to do ad hoc analysis queries, etc.

Of course in the UI one can simply flip signs on credit-normal accounts to avoid displaying negative numbers if one wishes.

Replies

jltsiren • 01/03/2026

Negative numbers are probably convenient, if your background is in a field, where numerical calculations are the norm. Traditional accounting is better justified from a mathematical perspective, as mathematics is more about definitions than calculations.

There are usually multiple levels of abstraction in code. When choosing the one to use for a particular task, it's a good idea to prioritize both simplicity and conceptual clarity. Bad things often happen, when the two priorities disagree. And you should try to use the same terminology and same concepts as the user as much as reasonably possible. Otherwise it's easy to make wrong choices by thinking about the problem from a wrong perspective.