KWITO is a simple online invoicing app for Polish sole traders, freelancers and small businesses. It issues VAT invoices and corrective invoices, sends them to KSeF - Poland's mandatory National e-Invoice System (API 2.0, FA(3) schema) - and downloads purchase invoices from KSeF several times a day. Customer data is filled in automatically from the Polish business register (GUS) by tax ID (NIP). Invoices go to customers by e-mail or SMS, recurring invoices are issued automatically (weekly, monthly, quarterly, yearly), OCR reads paper invoices photographed with a phone, and a monthly summary of sales and purchase invoices is e-mailed to the company's accountant on the 1st of each month. A KSeF demo mode lets new users practise sending invoices without connecting to the Ministry of Finance. The free Starter plan includes KSeF and up to 3 invoices a month; Pro costs 19 PLN net per month with unlimited invoices. The app interface is in Polish.