QuickBooks Online uses the first row of your spreadsheet for mapping and doesn't import its content. If you need the information from the first row of your file, add a header row to your spreadsheet, or duplicate the first line before importing the file.
If your version of QuickBooks Online supports multicurrency, your home currency is assigned to all customers and suppliers by default. If a change in customer or supplier currency is necessary, select the Currency column and choose the currency you want to associate with the contact on the Review screen while importing your list.
If you have imported your products and services incorrectly, don’t worry — you can overwrite all values for each product or service that you import with the identical name. Just import the same file again and select Overwrite all values at the bottom of the page.
Note: Once you select Import, this overwrite cannot be undone.
It is not possible for you to merge multiple QuickBooks Online companies into one. However, you can consider using Qvinci Consolidations, which is our authorised 3rd party app. Qvinci can sync data from QuickBooks files in many locations, allowing you to consolidate and compare companies easily.