Can I add a service/labor charge to an invoice that is a percentage of the pretax subtotal? How do I do that?

Thanks for posting here in the Community, @burningcedarfood.

You can manually add the service/labor charge to your invoice. Though, you need to manually calculate the percentage of the pretax subtotal and add them as a service fee in your invoice.

To get started, let's create a service fee item to your Products and Services. Let me show you how:

1. Go to Sales then choose Products and Services.
2. Click on New then select Service.
3. Enter the name of your service item.
4. Select the account you'd use to track our processing fees under the Income account drop-down.
5. Once done, click Save and Close.

Once done, create a new invoice for the fee and send it to your customer. 

Here's how:

1. Click + New.
2. Choose Invoice.
3. Fill out the invoice.
4. In the Product/Service dropdown, choose the fee item you created.
5. In the Amount field, enter the amount of the service fee.
6. Once done, hit Save and send or Save and close.

For complete details, see this article: Manually add service fees to invoices in QuickBooks Online.

For future use, here's a guide to learn more on how to manage sales forms in QBO: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Please keep in touch if there's anything else I can do to help you succeed with QuickBooks. I've got your back. Have a great day.