GST filing for every client, without the Excel matching

The problem

A CA firm files GST for dozens of clients every month. For each one, staff collect invoices, download supplier data from the government portal, compare the two in Excel, chase mismatches, accept or reject entries, then file.

Hundreds of invoices per client, the same steps every month, hard deadlines.

What I found

The first version could do every step, and it was hard to use. Everything sat on one screen.

The GST month already has a shape, set by the deadlines: invoices by the 10th, actions by the 13th, supplier data on the 14th, filing by the 20th. Staff weren't asking what the tool could do. They were asking which client is behind, and on what.

Key decisions

Built around the calendar

Each client's month is a four-step workflow that follows the deadlines. Steps guide; they don't lock, because accountants often work ahead.

AI reads, people check

Printed and handwritten invoices are read by AI. GSTINs are validated and every manual edit is marked.

Careful matching

Match on GSTIN and invoice number first. Use the amount only when exactly one invoice fits. Exact matches are accepted automatically.

Clients upload directly

Businesses upload invoices to their own portal, and the firm can email each client what is still pending.

Months can close with known gaps

Closed months turn grey, not red, so the dashboard shows only what still needs action.

How it's built

Stack

Next.js on Cloudflare with D1 and R2 for the firm workspace and client portal.

Portal agent

An Electron desktop app drives the GST portal with Playwright from the firm's own computer. It re-reads live portal state before submitting, so it never overwrites a newer decision. Queries went from 8–20 seconds to 1–3.

Invoice reading

Mistral OCR extracts invoice fields. Credit notes are matched with the correct sign.