Does not let me create Estimates poppinf a notification of Transactions can have only one foreign currency at a time

Hi there, @marianna-carmel-.

You'll need to turn on the Multicurrency feature in QuickBooks Online. Please keep in mind that you can only turn on multi-currency for new customers. For customers that are already in your QuickBooks, the "This customer pays me with" option is greyed out.

To turn on multi-currency:

1. Go to the Settings icon and select Company Settings.
2. Select Advanced and in the Currency section, click Multicurrency.
3. Check the box labeled Multicurrency to turn this feature on. Note: Once multicurrency is turned on, the home currency is set and cannot be changed in QuickBooks Online.
4. Click Save, then Done.

Once turned on, you need to set up your customer for multicurrency. Whenever you create invoices, it will automatically detect its currency.

1. Go to the Sales tab and select Customers.
2. Click New customer.
3. Fill out the Customer Information window.
4. Click the Payment and billing tab.
5. Click on the drop-down under This customer pays me with, and select the correct customer currency.
6. Click Save.

You can check out these links to learn more information on how Multicurrency works in QBO:

• Multi-currency FAQ
• Assign a foreign currency or multicurrency to a customer

Feel free to reach out back to me if there's anything else you need.