Is it possible for clients to begin filling out the form, save it, and go back to fill it out at a later date?

It is possible to save a form and continue later. You might consider using one of the following options:

1. How to Enable Auto fill feature - save form entries to continue later

Auto fill method is based on a browser local storage. It is saving the form data on the user's browser, so the user can open the form later and he/she will see the past data. Note - the user will need to use the same browser to access data.

2. How to Save Forms and Continue Later (Session method)

The Session method is saving the data on our servers. With this method, you will need to use two forms, one for session generation and second as primary. Then users will be able to access their sessions from any locations.

Hope this will help. Let us know if you need further assistance.