Hello, @Anonymous1.

You can import your invoice in your QuickBooks Online via CSV file. 

Let me help you how.

1. Go to Settings ⚙ 
2. Select Import Data.
3. Click Invoices.
4. Select Browse and then find and select the spreadsheet of your invoices
5. Select Next.

Once done, map your import fields.

1. Map the column headers with invoice fields in QuickBooks. Fields with an asterisk (*) are required.
2. Select Not applicable for any fields not in your spreadsheet.
3. Select the date format you used, like DD/MM/YYYY.
4. Select Exclusive or Inclusive as your tax option.
5. Select Next.

After you map the fields, review the summary of your import. If everything looks good, select Start import. Then, select OK if all your invoices are imported.

You can refer to this article for additional information on how to import multiple invoices at once. Import multiple invoices at once.

Feel free to leave a comment below if you have any other questions. Take care!