Hello Juice Tin,
Welcome to Community! I appreciate the concerns you have when it comes to foreign currencies in QuickBooks Online. I would be happy to provide some insight here!
Once multicurrency has been turned on, you can assign currency to your accounts. Your chart of accounts will show account balances in their assigned currency and will have a column identifying the currency for each account. Please note that income and expense accounts always use your Home currency.
Here's how to add a foreign currency account;
1. Open your Settings ⚙ and select Chart of Accounts
2. Hit New
3. Use the ▼ dropdown menu to select the appropriate Account type and Detail type
4. Enter a Name for the account
5. Choose the currency for the account from the Currency ▼ dropdown menu
6. Hit Save and close.
In addition, you can set a default currency to your customers and suppliers.
If you have any other questions or concerns, feel free to reach back out. We would be glad to assist!