Can you connect Quickbooks to Revolut Business? It assumes that my account is in another currency than my base (EURO) although it isn't, forcing me to upgrade.

Yes, you can connect QuickBooks to Revolut Business, accounts. 

So you won't have to manually enter your transactions, you'll want you connect your bank or credit card account in QBO. To do that, here's how: 

1. Go to select Transactions, then select Bank transactions.
2. If this is the first bank account you’ve set up, select Connect account. Or select Link account if you already created one.
3. Search for your bank. 
4. Sign into your bank by entering your banking username and password. Then select Continue.
5. Follow the on-screen steps to connect. 
6. Select any accounts you want to connect like, your savings, checking, or credit card. Then choose the matching account type from your chart of accounts in QuickBooks.

Regarding the currency issue, QuickBooks assumes that each account is in a single currency. If you have accounts in multiple currencies, you need to enable multi-currency in QuickBooks. However, please know that multi-currency is available only to QuickBooks Online Essentials and Plus users. 

If you're not one of its users, consider upgrading or downgrade your QuickBooks Online subscription so you can start tracking your foreign currency transactions.

 Moreover, if your account is being assumed to be in a different currency, you might need to check your settings in QuickBooks. You can refer to this article to add a foreign currency account in QBO: How to add a foreign currency account in QuickBooks Online

Remember, once you turn on the multi-currency feature in QuickBooks, you cannot turn it off. If you’re unsure, it’s recommended to consult with an accountant. 

Don't hesitate to reach out to us if you have further questions about connecting accounts and currency in QBO. We'll always be here in the Community to help.