An Offline-First POS With Barcode Checkout and FBR Invoicing

A computer-accessories counter moves fast and carries a long tail of small, similar items — cables, adapters, memory, peripherals — where picking the wrong variant or mistyping a price is easy. Shops in this category often run sales through a generic invoicing tool or a spreadsheet, count stock by walking the shelves, and reconcile at the end of the day from memory and paper.

The brief added two hard constraints. First, the till had to work offline: a sale cannot wait for a router to reconnect, and cloud POS products that stall without connectivity were not acceptable. Second, invoices had to meet the requirements of FBR, Pakistan's Federal Board of Revenue, which sets specific invoice formatting and reporting rules for registered retailers. On top of that, the owner wanted plain reports — daily sales, stock levels, best-selling items — without exporting anything to another program.

We built the POS as an Electron application with a React front end and a local SQLite database, which gives the shop a proper desktop program on its existing Windows PC. Everything the counter needs — product lookup, cart, payment, receipt — runs against the local database, so checkout speed and availability do not depend on the network at all. React keeps the checkout screen responsive and easy to extend, and Electron packages the whole thing into an installer the owner can set up on a second machine.

Checkout is barcode-led: scanning an item adds it to the sale at its current price, and completing the sale decrements stock. The inventory module holds products, variants, cost and selling prices, and quantities, with low-stock visibility so reorders happen before an item runs out. The invoicing module produces FBR-formatted invoices at the point of sale, and the reports section summarizes sales by day, product and period so the owner can close the day from one screen.

SQLite was the right store for this job: a single local file, no database server to run, fast enough for a busy counter, and simple to back up. The architecture also leaves a clear path to sync — because the app owns its data locally, a later step could push sales and stock to a central store whenever a connection is available, without changing how the till works.