Why can't I change the main currency?

Because every amount and every exchange rate you have saved is measured against it. Once bookings, payments, invoices, supplier costs or rate history exist, changing the main currency would silently make all of them wrong, so the system refuses. Before that, while you are still setting up, you can change it freely.

Where it is set

Settings → Agency and brand, field Main currency (Prices, invoices and reports use it). The list offers your current main currency and the currencies on Currencies. When you save a new one, the window Change the main currency? asks you to confirm: Amounts already saved are not converted. Change it only before you start selling, and update the exchange rates in Settings → Currencies. Press Change currency.

On Settings → Currencies the note at the bottom says the same: the base currency is set on the agency page and cannot change once money is recorded.

When it is refused

You see one of these messages, and nothing changes:

• The base currency cannot change once bookings, payments, invoices or supplier costs are recorded: their saved exchange rates are against the current base. Report in another currency instead (Reports → currency). This applies as soon as one booking, payment, invoice or supplier cost exists, even a test one.
• The base currency cannot change once exchange rates have a history: past rates are against the current base. Report in another currency instead. This applies as soon as one rate was typed, imported or copied with Update rates, including the rate you type when you add a currency. Starting rates set by the system do not count.

What happens when it is allowed

• Every currency on your list is restated against the new main currency, so the rates between currencies stay the same. For example, with BHD as main currency and SAR at 0.1003 BHD, switching to SAR makes SAR 1 and BHD about 9.97 SAR.
• The new main currency gets rate 1 and is switched on. The old one stays on the list as an ordinary currency.
• Starting rates the system had set against the old main currency are dropped from the history.
• Check the rates on Settings → Currencies afterwards, and set Decimals on the agency page if the new currency uses a different number (3 for dinars, 2 for riyals and dirhams).

What to do instead

• Show reports in another currency. On Settings → Currencies, set Reports open in to the currency you want reports, the dashboard and the owner's phone to show first. Each person can also switch the currency on those screens.
• Sell in another currency. Add the currency with its rate and price trips in it. Each record keeps the rate of its day.
• Work in another country. Add a branch there: each branch has its own currency for its documents. See Branches.