GnuCash

Most budgeting apps keep a running list: log an expense, tag it, look at a pie chart at month end. GnuCash does actual double-entry bookkeeping — every amount is recorded in two accounts at once, one decreasing as the other increases. Salary arriving is "bank balance up, income up"; a card purchase is "expense up, credit card liability up".

Learning the method costs a few evenings, but it gives you something a running list cannot: books that check themselves. Assets equal liabilities plus equity, and when the equation does not balance you have mis-entered something and the software says so. For anyone seriously managing assets, credit cards, loans and investment holdings, that is worth real money.

Coverage is thorough: multi-currency with automatic conversion, stock and fund holdings with automatic price retrieval, scheduled recurring transactions, invoices and receivables, loan amortization schedules, plus proper balance sheets, income statements and cash flow reports. A small business can run legitimate books on it.

Data stays entirely local. The ledger is a file — XML or SQLite — that you store and back up however you like, with nothing uploaded, no account, and full functionality offline. That has become rare in finance software.

Two things to be clear about:

• The barrier is accounting concepts, not the software. If debits and credits are new to you, the first few days are uncomfortable. The official tutorial is good and worth two hours before you start.
• The interface is traditional desktop styling — powerful but not modern-looking, which is what a twenty-year-old project tends to look like.

If all you want is to note what you spent today, Actual Budget or a simple phone app fits better. GnuCash is for people who want household finances kept as real books.