You can create a checklist from scratch or provide a template that will autofill each item. These checklists can be assigned to the Client or an internal user.
Client Checklist tab overview
When you click the Checklist tab you can add individual items by choosing Add Item.
Type in your item, Select the Assignees, Due Date, and then choose the Green Checkmark.
You can use a checklist template to autofill
Click the clipboard button next to the green checkmark.
Refer to How to add/edit Checklist templates for more information on creating these templates.