We can customize the invoice form through the Custom Form Styles page, cortekair.
We can add a custom field for the work description of your invoice form. Let me guide you with these steps:
Before doing so, we'll need to turn on the Custom fields option first. Here's how:
Afterward, you're good to a custom field on the invoice form.
I've also added this article if you want to let your customers pay the invoices online: Create an invoice your customer can pay online.
Don't hesitate to tag my name if you still have other concerns. I'm here to help you!