If the sales order is in EUR but the client want to be invoiced in USD, how do you handle this in NetSuite? Thank you.

@Luis currency will remain same across transactions (from SO to Invoice) as per my understanding. You cannot update currency on SO once the SO is created so maybe you need to either find a way to enter the SO in USD at the start (with exchange rate of the given date when SO is created)..or you need to something in the payment capture piece after Invoice is completed