Offline Invoice Generator Desktop App with GST Billing and Sales Reports (Electron)

Small shops, freelancers and service providers across India must issue GST-compliant invoices, but the tools available to them are a poor fit: cloud billing apps need a permanent internet connection and charge monthly subscriptions, while Excel-based billing relies on hand-typed tax math that routinely gets CGST/SGST splits, round-off and HSN codes wrong. InvoiceDesk is an offline-first desktop application built with Electron that fixes both problems at once. The invoice builder computes taxable value, CGST, SGST or IGST per line item automatically from the configured slab and the buyer-seller state combination, generates the invoice number sequence, converts totals to amount-in-words, and produces a print-ready tax invoice. A local client master, invoice history with paid/unpaid tracking, and a sales-reports dashboard with monthly revenue charts and tax summaries complete the package. All data stays in a local database on the user's PC — no account, no cloud, no subscription.

This is a built-to-order software project: the full Electron source, packaged desktop installer, demo data and the complete viva kit (report, PPT, Q&A) are prepared fresh for you.

The problem
Billing is where small businesses lose money quietly. A shopkeeper issuing twenty invoices a day on a spreadsheet multiplies quantity by rate by hand, looks up the GST slab from memory, and splits CGST/SGST on a calculator — every step is a chance to under- or over-charge tax, and mistakes surface months later during filing or audit. Cloud billing software solves the math but creates new problems: it stops working when the internet drops, which is routine in small towns and market areas; it stores sensitive sales data on someone else's servers; and it charges a subscription a two-person shop resents paying. Full accounting suites are powerful but expensive and intimidating for a first-time computer user. The gap is a simple, honest, offline billing tool: install it once, type items, get a correct GST invoice every time, and see at a glance how the business is doing this month. That gap is exactly what this project fills.

1. On first launch the app loads the seller profile (business name, address, GSTIN, home state) stored locally; this header prints on every invoice.
2. The user enters buyer details — name, address, state and optional GSTIN — or picks a repeat buyer from the client master.
3. Line items are added with description, HSN/SAC code, quantity, rate and GST slab; each row's taxable value and tax are recomputed instantly as values change.
4. The app compares buyer state with seller state: matching states split each row's tax into CGST + SGST; different states apply the full tax as IGST.
5. Subtotal, tax breakup, round-off to the nearest rupee and grand total are derived, and the total is converted to amount-in-words using the Indian numbering system.
6. Saving stores the invoice in the local database with an auto-sequenced number (INV/2026-27/0001 and on); the preview renders the formal tax invoice for printing or PDF export.
7. The reports dashboard aggregates all saved invoices into revenue statistics, a monthly stacked bar chart, top-client rankings and a month-wise CGST/SGST/IGST summary.

Tech stack:

• Electron (desktop application shell)
• JavaScript, HTML5, CSS3 (renderer UI)
• Node.js (main process)
• SQLite via better-sqlite3 (local database)
• Custom SVG charting (reports dashboard)
• Print-to-PDF export (invoice output)
• Electron Builder (Windows installer packaging)
• Git (version control)

• [Automatic GST calculation engine] Every line item computes taxable value and tax from quantity, rate and the selected 0/5/12/18/28% slab; invoice subtotal, tax breakup, round-off to the nearest rupee and amount-in-words are derived automatically, never typed.
• [Intra-state vs inter-state tax logic] The app compares the seller's state with the buyer's state: the same state splits tax equally into CGST + SGST, different states apply IGST on the full amount — matching how GST actually works.
• [Client master with GSTIN records] Buyer name, address, state and GSTIN are stored per client, so repeat billing becomes a selection instead of retyping, with GSTIN format validated on entry.
• [Invoice history with payment tracking] Every saved invoice is listed with taxable value, tax breakup and grand total; invoices can be marked paid or unpaid and searched by client name or invoice number.
• [Sales reports dashboard] Saved invoices feed live stat cards (revenue, invoice count, GST collected, average invoice value), a six-month stacked revenue chart, top-client rankings and a month-wise tax summary.
• [Print-ready tax invoice] One click renders a formal tax invoice — business header, billed-to/billed-from blocks, HSN-wise item table, tax breakup, terms and signature block — ready for printing or saving as PDF.
• [Offline-first local storage] All invoices, clients and settings live in a local database on the PC; the app works fully without internet and no sales data ever leaves the machine.

• Complete Electron application source (main + renderer processes, documented)
• Packaged Windows installer built with Electron Builder
• Seeded demo dataset (sample business, clients and invoices) for evaluation
• Project report PDF (architecture, GST logic design, database schema, testing notes)
• PPT presentation for the final review
• Viva Q&A preparation document (Electron architecture, GST rules implemented, offline storage design)
• User manual: installation, daily billing workflow, and backing up the local database