Should be a built-in way to enter Service From and To date range on an Invoice.

A pleasant day to you, @sagesmith.

At this time, being able to add a service From and To date range on an invoice template isn't available in QuickBooks Online. The service date that you can select is on the day that the product/service was purchased or made. 

To indicate the date range of your sales transaction, you may enter them on the description box. Please see the screenshot attached for reference: 

Having the option to add the duration of the service date in the invoice template is a great idea. I'll share this preference to our developers, so they can assess the suggestion and put it under consideration.

To learn more details about the customization that you can apply on your sales forms, please check out this link: Customize your invoices, estimates, and sales receipts in QuickBooks Online.

I also encourage you to visit our QuickBooks Online Blog to be updated with our latest news and enhancements. 

I've got your back if you have any other concerns. I'm always available to help. Happy Monday!