Free, cross-platform and offline-first invoicing solution that syncs.
Stripe Dashboard for iPhone - Track and manage payments on the go
Slimvoice - Insanely simple invoicing
Stripe - Online payment processing for internet businesses. Stripe is a suite of payment APIs that powers commerce for online businesses of all sizes. Use Stripe’s payment platform to accept and process payments online for easy-to-use commerce solutions.
Envoice - Send invoices and get paid on Paypal, Payoneer, Stripe and Square.
RevenueCat - In-app subscriptions made easy
Zoho Invoice - 100% free online invoicing software for small businesses.