Hi there,
Keeping your books organized is what QuickBooks Online is best at, and I can see why you'd like to merge two suppliers together for a tidy supplier list. If you're working with two suppliers that have different currencies, you'll receive the error message you've shared above. I'd be happy to shed some more light on this.
As explained in the error message you received, you're unable to merge suppliers with different currencies. Once you enter a supplier into QBO, you're unable to change or modify their default currency. This is to ensure that any data entered so far in QBO isn't impacted by these types of changes.
Working with multiple currencies can be complex on the back-end of your bookkeeping process, which is why you're unable to merge the two suppliers or change their currency.
I hope this helps shed some light on things for you. If you have any other questions, please don't hesitate to reach out to our tech support team.
Have a great day.
