Thanks for joining this 1099 discussion, @Rattledbythedetails.

To add the vendor's W-9 in QuickBooks Online, you can enter it manually. Here's how:

1. Go to the Vendors menu and then select Vendors.
2. Click the vendor's name, then Edit.
3. Enter the Company, Complete name, Business ID No.(Tax ID No.), and address.
   
4. Click Save.

You'll want to read these related articles to learn more:

• How to set up contractors and track them for 1099s in QuickBooks
• Fill out a W-9 and view your 1099-MISC
• E-file through the 1099 E-File Service (QuickBooks Online).

Please come back here if you need further assistance with QuickBooks and other payroll forms. I'll be right here if you need anything else.