Thanks for joining this thread, JamesCrozier.

Allow me to chime in for a moment and share some information about the issue you’re currently experiencing with the sales templates.

We have received reports from some customers that the invoices they created from estimates are displaying differently compared to their imported templates. Our engineers are working hard to come up with a resolution as soon as possible.

I suggest reaching out to our QuickBooks Online Customer Team to add your company to the notification list of affected users. You will also receive an email notification once there’s progress.

To reach them:

1. Go to Help at the top, then click on the Contact Us link.
2. In the How can we help? window, enter contact support in the field box.
3. Choose a way to connect with us.
4. Select Start messaging/We'll call you.

Rest assured, I'll keep you posted here in this thread for any updates available.

For future reference, check out this link with detailed information on how to create and use a custom form style.  

That should point you in the right track.

I appreciate your patience while we look into this. If there’s anything else I can help you in QBO, post a comment below. I’ll be right here to assist you further.