Multiple currencies

Each account has its own currency. If you only use one, there’s nothing to configure. As soon as a second account uses a different currency, Arca needs an exchange rate to work out your net worth and reports in a common base currency.

Setting an exchange rate

From Settings → Exchange rates, enter how much 1 unit of each currency is worth in your base currency. Every conversion (net worth, reports, transfers between accounts in different currencies) relies on these rates — Arca doesn’t fetch them automatically.

Missing rate

If a needed rate isn’t set, Arca flags it right where it matters:

• on the Accounts page, a “Missing rate: {currencies} — net worth approximate” badge,
• on Reports, the same warning for converted amounts,
• during a transfer between two accounts in different currencies with no rate set: the received amount equals the sent amount (no conversion), with a prompt to set the rate in Settings → Exchange rates.

Budget currency

This is the currency your net worth and reports are totaled in. It isn’t a setting: Arca derives it from your accounts. It’s the currency of the oldest account that is still open and on budget.

To change it, change which account it comes from — there is no toggle. There used to be one, next to language and theme; removing it was deliberate. It looked cosmetic, yet changing it silently pushed every account in a different currency out of the budget. Settings → Preferences now shows the currency without letting you edit it.

The amount is frozen when you record it

When a transaction lands on an account whose currency differs from the budget’s, Arca also stores its converted amount as of that moment.

The intended consequence: your past reports stop moving when a rate changes. A $100 expense recorded in January stays worth what it was in January, even if you fix the rate in June.

• Flows (spending, income, reports) use the rate frozen at entry.
• Account balances use today’s rate, because they represent money actually sitting there.

The gap between the two isn’t a rounding bug — it’s your foreign-exchange gain or loss.