Wave

Wave completely disrupted the bottom end of the billing market with a highly aggressive, deeply appealing strategy: their core invoicing and accounting software is absolutely, 100% free forever. It does not limit the number of invoices you can send, nor does it limit the number of clients you have. Because it is genuinely free, it is the absolute default starting point for millions of brand-new startups, side-hustlers, and gig workers who cannot afford a $30/month QuickBooks subscription. Wave makes its money entirely on the backend through payment processing fees. If a freelancer sends a free invoice and the client clicks "Pay via Credit Card," Wave takes the standard 2.9% transaction fee. Despite being free, the invoices look highly professional and modern. A user can upload their logo, select an accent color, and generate a beautiful PDF or web link in seconds. It completely legitimizes brand-new small businesses, allowing a person working out of their garage to send invoices that look like they came from a Fortune 500 agency.