Can we update an invoice later on with the tracking number?

Hello, laura.d@serax.co. Thanks for reaching out here in the Community. Allow me to share some information about your query.

Yes, you can add the tracking number later in your invoice. To proceed, turn on the Custom transaction numbers feature on the Account and Settings page.

These are the steps:

1. Go to the Gear icon 
2. Under Your Company, select Account and settings.
3.  On the Sales tab, click Sales form content. 
4.  Toggle to turn on the Custom transaction numbers.
5.  Click Done.

By doing the steps mentioned above, rest assured you’ll be able to add the tracking number later and then send the invoice to your customer.

You might want to give this article a visit, it’s about how to record invoice payments in QuickBooks Online.

You can always notify me if you have any other QuickBooks questions. I'm a few clicks away to help. Keep safe.