Most invoicing tools make your client create an account, or sit between you and your money. PayUp does neither, and it's free. Send a link your client pays by card, no signup, no app, no friction. The invoice marks itself paid the second the money moves, and chases late payers for you. Payments land directly in your own Stripe account; I never hold them and take no cut. No tiers, no upsell, no "upgrade to send more than 3 invoices."
