Invoice Maker: Offline invoices in one file. Pay once, keep it.

I made Invoice Maker for independent designers and consultants who want a simple invoice file they can keep on their computer. Open the file in a desktop browser, enter an invoice, and print or save a PDF. It supports USD, EUR, GBP and ILS and A4 or Letter printing. The invoice file works offline. Purchases and the optional enquiry form use online services. Invoice data is saved in your browser on that device; keep exported PDFs separately. This is an invoice document tool, not accounting software or a tax-certified e-invoicing service. There are free invoice tools; this is a paid option for people who prefer to keep a downloadable file. Which part of invoicing takes you the most time: entering details, calculating totals, or formatting the PDF?