Besides reducing errors, double-entry bookkeeping allows you to follow money flow easily, detect unexplained billings, and get all kinds of reports quickly, like profit & loss or financial statements.
However, to "deploy" it in full power, you must think like an accountant: money (or any other commodity) had to come from somewhere and had to go somewhere. Approaching this way, you can apply it in all sorts of things, like tracking income/expenses, car/house/equipment depreciation, fuel spending... I even tracked gym workouts for some time.
What works for me is ledger-cli [1]. It takes some time to get used to, especially for those who used GUI, but you get powerful reporting and extreme flexibility. For example, you can accept payments in bitcoin, return change in USD, and buy some stocks in EUR with the received money. A nightmare for other tools.
However, to "deploy" it in full power, you must think like an accountant: money (or any other commodity) had to come from somewhere and had to go somewhere. Approaching this way, you can apply it in all sorts of things, like tracking income/expenses, car/house/equipment depreciation, fuel spending... I even tracked gym workouts for some time.
What works for me is ledger-cli [1]. It takes some time to get used to, especially for those who used GUI, but you get powerful reporting and extreme flexibility. For example, you can accept payments in bitcoin, return change in USD, and buy some stocks in EUR with the received money. A nightmare for other tools.
[1] https://www.ledger-cli.org/