Saving an uncompleted form

Can my customer save their work if they have begun to complete the form, and want to return and finish it at a later time? Thank you.

They can, there are two methods for this purposes:

1) Saving data in users browser local storage: https://www.jotform.com/help/227-How-to-Enable-Auto-Fill-on-Forms 

2) Through a session, which allows then to continue from any device and browser: https://www.jotform.com/help/97-How-to-Save-Forms-and-Continue-Later 

Let us know if you need more help.