If I stop paying, do I lose my data?

No. If a paid plan or your trial ends, the workspace auto-drops to Free and nothing is deleted. Your records stay put — you just operate within the Free limits (3 clients, 3 projects, 5 invoices/month) until you upgrade again.

And if you decide to leave entirely, the one-click JSON export means you walk away with everything. No hostage situations, no lock-in.