Answer
No. Any data you enter during your free trial is saved, so you can pick up where you left off after subscribing.
Desktop app
Your trial data is stored on the computer you have been working on. Once you have purchased a subscription, use the Licence Assistant (accessible from within the program) to download and install your new licence. The program will then run as the full paid version using your existing data — nothing is lost.
See I Have Paid For My Licence — What Happens Next? for the step-by-step activation process.
Online (web/mobile) app
Your data is stored securely on our servers. When your subscription is active, it is picked up automatically the next time you log in — no manual licence entry is required. Your data remains intact throughout the transition from trial to paid subscription.
For more information on starting a trial, see Can I Try Lightning Payroll?