Hello there, @PWIA.
Currently, importing data to QuickBooks Online (QBO) will not update the old customer information. However, it'll add up to the existing lists.
Here's how:
- Go to the Gear icon.
- Under Tools, select Import data.
- Select Customers and select Browse to upload the file from your computer.
- Choose the file, and select Open.
- Select Next.
- Match your field to the corresponding QuickBooks Online field.
- Follow the prompts.
- Once done, click on Import.
You can refer this link for more information on how to import your customers list in QuickBooks: Import customers or vendors from email contacts to QuickBooks Online.
Visit this article to enter, edit, delete, or merge customers in QuickBooks: Add and manage customers in QuickBooks Online.
Keep me posted if you need additional help managing your customer info in QuickBooks. I'll be around to help. Have a wonderful day.
