gInvoice

Estimates and invoices that take seconds, not spreadsheets. Built and shipped by devShakib.

gInvoice is a billing app for people who run a business from their phone. Build an estimate, convert it to an invoice, track what is paid and what is overdue, and send a professional PDF without touching a spreadsheet. I built the Flutter app across iOS and Android — client and item catalogues, tax and discount handling, PDF generation and templating, and offline-first local storage.

Invoicing looks like formatting and is mostly rules. Numbering is frequently required to be sequential and gapless by tax authorities, which conflicts with offline-first — two devices cannot both claim number 47, so the identifier has to be assigned in a way that survives generating one on a plane.

Tax is the other half. Where it applies, at which rate, and whether rounding happens per line or on the total are jurisdictional questions with different right answers, and rounding at the wrong step produces totals that disagree with an accounting system by a cent. PDF matters because the invoice has to look identical everywhere it is opened.

Currently shipping version 1.0.2.