For the Lightning Payroll desktop application, the data you enter into your free trial will be saved on the computer you've been working on, even after your free trial expires. This means that if you decide to purchase the program after the free trial expires, you will be able to pick up where you left off and continue entering data without losing what's already been done.
The trial version of the program you've been using will be unlocked and able to be used as the full version once payment has been made and your subscription ID is entered into said trial version.
The same applies for the mobile and web versions of the program: the data will be saved, and you'll be able to pick up where you've left off after your subscription details have been entered.