Customers, stock and invoices live in spreadsheets

You dictate or you type, and the record creates itself.

A run through the app, demo data: a request typed to the assistant, the customer and invoice it creates, the invoice list with payments applied, the invoice finalized, the customer record and its PDF.
The assistant panel, demo data: a request typed in one line, the customer and the invoice it created, and, above, the confirmation it asked for before deleting a draft.
The customer record, demo data: total invoiced, amount collected, balance due, the finalized invoices with their PDF button, and the payments.
The invoice list, demo data: status (draft or finalized), total, amount paid and remaining balance, with each customer’s payments applied to the oldest invoices first.
The invoice PDF preview, demo data: header, customer block, product line, totals before and after tax, and payment status.

The problem

Small B2B companies juggle clients, stock, invoices and payments in spreadsheets, often with two tax regimes (before and after VAT).

What I built

A Next.js app for clients, products, stock, invoices and payments, working in both tax regimes. A Claude assistant with about 20 tools creates and updates records by text or voice, and asks before deleting anything.

Technical details

Row-level security on the data tables, join tables included
Streaming tool use (SSE) with about 20 declared tools
One set of routes serves both tax schemas
Voice input and output

Stack

Next.js 15
React 19
Supabase
Claude API
FastAPI + WeasyPrint

The result

Each payment is applied to the oldest unpaid invoices automatically, and invoices come out as PDFs.

A similar project in mind?

Tell me about your business and when you need it. You get a proposal by email.

I want this system

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