I can share some information about updating your customer information by importing, @GLP2020.

You can import your customers' list in QuickBooks Online (QBO). However, please take note that imported lists will not replace the old information but will add up to the existing lists on file. 

Check the following information in your spreadsheet before importing to QBO:

• The column headers are in the first row.
• Your contacts are on Sheet1 of the spreadsheet.
• The spreadsheet doesn't have any formulas, charts, or blank rows.
• The spreadsheet doesn't have any errors, such as #REF!, #NAME?, #N/A, or #VALUE!.
• The names don't contain colons (:) or quotation marks (").

Here's how to import the file:

1. Go to the Gear icon ⚙ and select Import Data.
2. Click on Customers and select Browse to upload the file from your computer. Choose the file, and select Open.
3. Select Next.
4. Match your field to the corresponding QuickBooks Online field.
5. Follow the prompts.
6. Once done, click on Import.

You can refer to this article for more information on how to your customers list in QBO: Import customers or vendors from email contacts to QuickBooks Online.

For visual reference about updating your customer's address and any other information, check this article: Edit customer information.

Here's also an article to answer the most commonly asked questions about importing data to QBO: FAQs about importing data to QuickBooks Online. It includes topics about other lists that you can import to QBO. 

Let me know if you need further help updating your customer information by leaving a reply below. Keep safe and have a wonderful day!