Indian retailers and restaurants run their billing counter under real regulatory pressure: every invoice must carry the correct CGST/SGST or IGST split, the right HSN/SAC code, an accurate place-of-supply, and — once you cross the e-invoicing turnover threshold — a valid IRN and signed QR from the IRP before the customer walks out. Stock ERPNext gives you the POS Invoice and Sales Invoice DocTypes, Item Tax Templates and GST fields, but the native POS flow was not built to enforce this at the counter in real time. Cashiers pick the wrong tax template, inter-state versus intra-state tax gets decided by hand, composition-scheme dealers still see tax lines they legally cannot charge, and IRN generation happens (if at all) as a separate back-office step long after the sale.

ECOSIRE builds a dedicated Frappe app — its own module, DocTypes and hooks — that closes those gaps directly inside the ERPNext POS. We add place-of-supply resolution as a server-side function wired through hooks.py doc events (validate / before_submit on POS Invoice and Sales Invoice) that compares the company GSTIN state code against the customer's billing/shipping GSTIN or state, then deterministically applies CGST+SGST for intra-state and IGST for inter-state — so the cashier never chooses. HSN/SAC codes are mapped from the Item master and validated against tax rate, with a client script that blocks submission when an HSN code is missing or its rate disagrees with the applied Item Tax Template. A whitelisted server method calls the IRP/e-invoice API to fetch the IRN and signed QR, stamps them onto the invoice, and renders the QR on the thermal/A4 print format; failures are logged to a custom E-Invoice Log DocType with retry via a scheduler event so a network blip never blocks the queue.

Composition-scheme billing is handled as a first-class mode: for a registered composition dealer the app suppresses tax lines on the customer-facing bill, prints the mandatory "composition taxable person, not eligible to collect tax" declaration, and keeps the internal turnover accounting intact for the quarterly CMP-08 view. Role profiles and permissions are set so counter staff can bill and generate IRNs but cannot edit tax rules, HSN maps or GSTIN configuration; those stay with the accounts/admin role. Everything is exposed cleanly over the Frappe REST API and whitelisted methods so your POS terminals, kitchen display, or a headless front-end can drive it, and the whole app is packaged as a versioned Frappe app compatible with ERPNext/Frappe v15 and v16.

Because this is build-to-order, nothing ships until we agree on scope. We start with a short scoping call, confirm your GST registration type, turnover/e-invoicing applicability, IRP credentials path, print formats and terminal setup in a written scope, then build against that. Typical delivery is one working week from confirmed scope. You get the installable source for your version, a UAT pass on a staging bench with a rollback plan, install and configuration on your instance, documentation, a training session for counter and accounts staff, a post-go-live support window, and the git repository handed over so you own what we built.