Hello @supplier,

Welcome to the Community. I can assist you with your concern about the invoices in QuickBooks Online.

Your products and services on an invoice will automatically follow the customer's currency. The option to have two different currencies on a single transaction is unavailable.

If you set up a customer with Euro, the system will show the same currency for all your products. The only workaround is to create two profiles for the British company.

You can separate the invoice for the products you sell in GBP and Euro. Here are some screenshots for your visual reference about how the currency affects an invoice:

Additionally, we've prepared answers to some frequently asked questions about using multi-currency in QuickBooks Online. For your additional reference, please check out this article: Multi-currency FAQ.

Comment down below if you have more questions or concerns about the process. I'd be glad to help you out.