Admins should create a custom permission set and assign it to the user(s) tasked with importing the firm's data. This permission set can later be de-activated.

How to Create a Custom Permission Set 

1. Enable: Set Audit Fields upon Record Creation under System Permissions. See this article for information about this setting.
2. Navigate to Setup > Permission Sets > New. Follow this article for more information about enabling these permissions. 
3. Name it Importing Permission Set. Select the license your users are assigned.
4. Select Save.
5. Navigate to System Permissions and enable the required permissions.
6. Enable "Set Audit Fields upon Record Creation" permission in System Permissions.
7. Assign this permission set to the user who will be importing your data into Litify.