Changes saved for invoice layout are not actually saving on the new invoices created.

Hi sarah125,

Welcome to the Community. QuickBooks Online is a great program that gives you the ability to easily track sales and expenses. I'd be glad to help.

If you added a box for PO# as a custom field, I encourage to follow these steps to ensure that the option "print on form" is enabled. 

1. Click on Gear Icon,
2. Select Custom fields,
3. Find the custom field name, click on Edit,
4. On All Sales forms, enable the  Print on form option if it's disabled.
5. Click Save.

The box for PO# will appear on the invoice.

Let me know if this helps!