Connect with and learn from others in the QuickBooks Community.
I'm here to help and ensure you'll be able to import your customized invoice template. Let's get this working for you.
You might want to make sure that the field for the tax amount has a number next to it so it will be mapped correctly. See the sample screenshot below.
If you still can't map the fields correctly, you can visit this link to help and guide you more in customizing and mapping your invoice template (proceed to Step 4): Importing Custom Invoice Templates into QuickBooks Online.
Additionally, you might find this article interesting about importing and designing your sales forms in QuickBooks Online: Import custom form styles for invoices or estimates.
You can always get back to me if you need additional assistance. I'll zip right back to help you out. You have a wonderful day!