Yes, the custom field feature is available in QuickBooks Online, capitolcollective.

I've got the steps so you can PO numbers to your invoices. You can start by following the steps outlined below:

1. Click the Settings ⚙ icon, then select Custom fields under the Lists column.
   
2. Select Add field if you need to enter a new one.
   
3. Choose Edit under Actions to modify the existing custom field.
   
   

You can refer to this link for additional information: Create and edit custom fields in QuickBooks Online Advanced.

To use custom fields on your reports, here are the steps you can follow:

1. Find and open the report you want to run.
2. Select the gear icon at the top right of the report.
   
3. Under Change columns, check the box for each custom field you want to add.
4. Select anywhere outside the settings panel to close it.
   
   

QuickBooks adds the columns to the right side of the report. To reorder the columns, select the gear icon again, then select Reorder columns.

Check out these handy articles for future guide:

• Filter, search, and sort with custom fields
• Customize reports in QuickBooks Online.
  
  

Keep me posted if you need anything else with QuickBooks. I'll be right here to help you.