Can expense receipts (from cash account) entered in £GBP be automatically converted to €euro ?

We're glad to see you here posting in the Community. I'll share information about the foreign currency function in QuickBooks.

With QuickBooks Online, the multicurrency function helps you handle your transactions and manage different currencies. Once this feature is enabled, QuickBooks uses exchange rates to get the home currency values of your foreign currency transactions. 

To answer your question, yes, expense receipts entered in £GBP will be automatically converted to €euro. If you want to enable this feature, you can follow the steps below.

Here's how:

1. Go to the Gear icon and select Account and Settings.
2. Choose Advanced.
3. Click Edit in the Currency section and choose your Home Currency.
4. Select the Multicurrency checkbox and confirm that you understand that you can't undo this option.
5. Once done, select Save and Close.

You can check out this article for more detailed information: Learn about exchange rates in QuickBooks Online.

Moreover, you'll want to browse this reference to guide you in reviewing your business finances: Run reports in QuickBooks Online.

If you have additional questions or other QuickBooks concerns, you can always leave a comment below. We'll always be here to assist you further. Have a good one!