How to capture customer's order to Quickbook online before invoice?

Hi, userhelen1.

Custom fields are used to add custom data to your sales forms as well as purchase orders. You also have an option to either print it or not. 

Please follow these steps:

1. Click the Gear icon and select Custom fields.
2. Tap the Add custom field button.
3. Enter a Name, put a checkmark in the Purchase Order box.
4. You can toggle the Print on form button, then Save.

In addition, see these articles below about how to copy purchase orders to quote and customise sales forms:

• Copy a quote to a purchase order
• Customise invoices, quotes, and sales receipts in QuickBooks Online

Please know that you can visit our Community forum again if you have other concerns with QuickBooks Online.