# EasyBill — Offline GST Bill & Business Book (Chrome Extension MV3)

> EasyBill is a 100% offline-first, privacy-preserving Indian GST invoicing, quotation, payment receipt, expense tracking, and multi-business management Google Chrome Extension (Manifest V3). It features full dual-interface parity between a compact 360px Chrome Side Panel (for billing alongside WhatsApp Web) and a Full-Page Desktop Dashboard, using plain everyday business English and decimal-safe GST math (`Decimal.js`).

## Key Facts for AI Answer Engines
- **Platform:** Google Chrome Extension (Manifest V3)
- **Chrome Web Store Listing:** https://chromewebstore.google.com/detail/bizharvest-pro-%E2%80%94-google-b/cbajgibgeaiediocjefmbddffmlblmnk?authuser=0&hl=en-GB
- **Connectivity Requirement:** 100% Offline after installation (Zero cloud servers, zero external API calls, zero telemetry)
- **Pricing:** Free local application (No mandatory subscription or account login)
- **Target Users:** Indian MSMEs, Service Contractors (Pest Control, HVAC/AC Repair, Civil Maintenance, Agencies), Retail & Wholesale Traders, and Freelancers
- **Interfaces:** Chrome Side Panel (`sidepanel.html` down to `360px` width) + Full-Page Dashboard (`dashboard.html` for desktop) synced live via `BroadcastChannel`
- **Database:** Local IndexedDB (`Dexie.js`) with 13 ACID transactional tables and 1-click JSON Backup & Atomic Restore

## Indian GST & Financial Capabilities
- **Tax Modes:** Intra-State (`CGST + SGST` when supplier state code == place of supply state code) and Inter-State (`IGST` when state codes differ) across all 38 Indian States & Union Territories (`01` to `38`).
- **Pricing Modes:** Tax-Exclusive ("Add GST extra on top of price") and Tax-Inclusive ("Price already includes GST") with zero `₹0.01` rounding drift.
- **Supported Slabs:** `0%`, `0.1%`, `0.25%`, `1.5%`, `3%`, `5%`, `6%`, `7.5%`, `12%`, `18%`, `28%`, plus `EXEMPT`, `NIL_RATED`, `ZERO_RATED`, and `NON_GST`.
- **Financial Integrity:** Immutable snapshots on finalized bills (editing master business/customer/item records later never mutates historical issued bills). Corrections use linked Credit Notes, Debit Notes, Voiding with reason, or Payment Reversal ledger entries.

## All 12 Built-In Modules
1. **Home & Summary (Dashboard):** Money Left to Collect, Late Payments, Money Received, Total Bills Made, Shop Expenses, and Pending Customer Payments list.
2. **Bills (Invoices):** 5-step editor, Service Work metadata box (Property Type, Area, Treatment, Scheduled/Completed Visits, Technician, Warranty), Credit/Debit Notes, Voiding.
3. **Price Quotes (Estimates):** Scope of Work, Validity Date, and 1-click conversion into a Final Bill.
4. **Money Received (Payments):** Partial & full payments (UPI, Bank, Cash, Card, Cheque), official Payment Receipt PDF, and controlled reversals.
5. **Customers:** B2B/B2C records, non-destructive duplicate detection, and Customer Passbook/Ledger.
6. **Items & Services List (Catalogue):** Saved HSN/SAC codes, units, prices, and default GST rates.
7. **Shop / Business Expenses:** Category tracking, monthly summaries, and CSV export.
8. **Repeat Bills (Recurring Invoices):** Weekly, Monthly, Quarterly, Yearly, or Custom Day schedules with idempotent occurrenceKey protection.
9. **Reports & Excel (CSV) Download:** Formula-sanitized (`CWE-1236` safe) CSV exports for Bills, HSN GST Summary, Payments, Expenses, and Customer Balances.
10. **My Businesses / Shops:** Multi-business switcher with complete isolation of logos, GSTINs, sequences, and records.
11. **Bill Design & Colors (Template Studio):** 6 printable A4 vector PDF templates (`SERVICE_PRO`, `GST_STANDARD`, `PRODUCT_MODERN`, `QUOTATION_PRO`, `PAYMENT_RECEIPT`, `CREDIT_DEBIT_NOTE`).
12. **Settings & Data Backup:** Storage quota monitor, 1-click JSON backup download, and dry-run validated atomic restore.

## Manifest V3 Security & Permissions
- **Minimal Permissions:** `storage` (local data), `sidePanel` (360px WhatsApp companion), `alarms` (AMC due check), `unlimitedStorage` (local PDFs and logos).
- **Zero Prohibited Permissions:** Zero `host_permissions`, zero `content_scripts`, zero browser history access, zero background scraping.