[omichowdhury]

The reason isn’t to double the amount the work to catch errors. storing both sides genuinely stores extra metadata about the transaction that is not captured by only storing it once.

In double-entry, you’re tracking two different things: - Your current net worth. These are tracked in State accounts (Asset and Liability). - The reasons your current net worth changed. These are tracked in Change accounts (Income and Expense).

Say $5 enters your bank account, that’s recorded as an increase in an Asset account. Whether your net worth changed or not depends on the reason. There’s lots of reasons that could have happened, and that’s recorded as the second entry: - Took out a loan: increase in Liability (no net worth change) - Got paid back for a loan: decrease in Asset (no net worth change) - Sold something: increase in Income (net worth did change) - Got a refund: decrease in Expense (net worth did change)

I agree that re-engineering accounting is necessary for software engineers to build financial systems. I think it’s time to ditch credits and debits and instead deal in State and Change accounts with negative numbers.

PS I go more into it here: https://news.ycombinator.com/item?id=39994335