Invoice Keeper: photograph a supplier invoice, check it, send it to your accounting system

Starting point

Small businesses receive supplier invoices as photos and PDFs, and someone types them into the accounting system by hand. It is slow, and the errors only surface weeks later at reconciliation. The product grew out of a real client workflow where exactly this typing was the bottleneck.

Solution

Typing becomes checking. A model reads the document and fills the form; a second pass reviews the extracted figures for the errors reconciliation would find later – line items that do not sum to the subtotal, a missing tax number, a due date before the issue date. The confirmed JSON is posted to a webhook the user configures, so it drops into whatever system they already use.

Implementation

The web app is built with Next.js, TypeScript and Tailwind and hosted on Vercel; the Android app with Kotlin, Jetpack Compose, Room and Retrofit. The app holds no API key at all: it calls the web app’s server routes, which keep the key server-side. Both applications work end to end against live AI calls and extract correctly from real German supplier invoices. Invoices and settings stay local in the browser or on the device.