I have customised the sales invoice via the Custom Form Styles function. The new field headings can be seen on the printable form but not on screen. Why?

Hi, there. I appreciate you getting back to us in this thread.

Currently, the ability to update the column header format you've created from the Custom Form Style settings is unavailable when entering your sales data on the invoice window. If the changes made from the new sales forms appear when previewing the invoice template or sending them, you don't need to worry. These modifications are set only to display when viewing and sending them to your customers. 

We'd love to hear about this feature request of yours. I'd suggest sending your feedback to product developers. They'll review your suggestion and include them in our future product enhancements.

Here's how to submit feedback:

1. Go to the Help menu and select Send Feedback Online.
2. Click on Product Suggestion and enter your feedback or suggestion.
3. Once done, tap Send feedback.

Moreover, I've added these references to guide you further in modifying your sales forms and on how to record invoice payments:

• Customise invoices, estimates, and sales receipts in QuickBooks Online.
• Record invoice payments in QuickBooks Online.

Let us know in the comments below if you have additional questions customising your invoices. We'd be delighted to hear more from you and assist you further. Have a good one!