Client Portal & GST Billing System

The business problem

A small services business usually runs on WhatsApp, email and spreadsheets. Each one causes a familiar problem: invoices with the wrong GST split, gaps in invoice numbering, payments that are hard to match to invoices, clients asking "what's the status?" because they cannot see it, and passwords for hosting accounts sent over chat. I wanted one system that does it properly, and I built it for my own business first.

What I built

Client portal. Each client signs in to see their own projects, milestones, tasks, files, invoices and support tickets, and nothing belonging to anyone else.

GST invoicing, built the way an accountant expects:

• GSTIN, PAN and state on every invoice; CGST + SGST for the same state and IGST for another state, chosen automatically.
• A saved service catalogue with SAC codes and rates, plus named discounts (NGO, festival offer) that print as their own lines.
• Financial-year numbering (BP/2026-27/0001) that restarts every April and never leaves a gap: issued invoices are cancelled, not deleted.
• Line amounts and GST keep their paise; only the grand total is rounded, with a visible round-off line, and the amount in words matches it.
• One click issues the invoice, emails a PDF to the client, and shows it in their portal.

Payments and receivables. Payments are recorded against the right project and invoice. An invoice marks itself paid when fully settled and overdue when its due date passes, so outstanding money is always visible.

Security that clients can trust. End-to-end encrypted chat and a credential vault: the server stores only ciphertext, so client passwords are never readable in the database, email or WhatsApp. Sign-in throttling, strict validation of every input and checked file uploads complete it, backed by more than 350 automated tests.

Why it matters to the business

• Fewer accounting errors: tax split, rounding and numbering are handled by rules, not memory.
• Faster billing and follow-up: an invoice takes minutes, and what is due or overdue is visible at a glance.
• Fewer status calls: clients can see progress, files and payments themselves.
• A stronger sales conversation: "you will see everything in your own portal" helps win work.

Where my accounting background shows

Most invoicing tools are built by developers who have never closed a month. Gap-free numbering, cancellation instead of deletion, paise-accurate tax lines and a matching round-off are the details an auditor or CA checks first. I built them in from day one.