Singapore finance teams running ERPNext hit a wall at two points: preparing the quarterly GST F5 return and adopting IRAS InvoiceNow. ERPNext core gives you tax templates and a generic Tax Detail report, but it has no concept of the GST F5 box structure (Boxes 1 through 8, plus reverse-charge and imported-services lines), no PEPPOL BIS Billing 3.0 UBL output, and no connection to a Peppol Access Point. So finance ends up hand-mapping account balances into the myTax Portal, and e-invoicing becomes a separate portal-upload chore rather than something that happens straight from a submitted Sales Invoice. As InvoiceNow moves from voluntary to phased mandatory for GST-registered businesses, that manual gap becomes a compliance risk.

ECOSIRE builds a proper Frappe app (its own module, DocTypes, and hooks.py) that installs cleanly alongside your existing ERPNext without forking core. On the GST side we add company-level GST registration fields (GST registration number, effective date, filing frequency), map your chart of accounts and tax templates to the F5 box logic, and generate a Singapore GST F5 Return DocType that computes each box (standard-rated, zero-rated, exempt, output tax, input tax, reverse-charge on imported services) with drill-down to the underlying GL entries so your accountant can reconcile every figure before filing. On the e-invoicing side, a submit-time on_submit doc event on Sales Invoice builds a PEPPOL BIS Billing 3.0 UBL document, validates it, and transmits it to the buyer through your Peppol Access Point over the standard AS4/Four-Corner model, writing back the transmission status, message ID, and any Access Point errors onto the invoice so failures are visible and retryable rather than silent.

Technically it is built the ERPNext-native way. Server scripts and hooks.py doc events drive validation and transmission; client scripts add the InvoiceNow status indicator and the "resend" action to the Sales Invoice form; whitelisted methods exposed over the Frappe REST API let your Access Point or middleware call back with delivery receipts; scheduler events poll for pending transmissions and stuck documents; and permissions are enforced through dedicated role profiles (for example a "GST Officer" role gated to the F5 return and an "InvoiceNow Operator" role for transmission monitoring). Reverse-charge and zero-rated scenarios are handled through configurable tax-template mappings rather than hard-coded rules, so your specific supply mix is respected. It targets ERPNext/Frappe v15 and v16.

This is build-to-order, not an instant download. We start with a scoping call to confirm your GST profile, Access Point provider, invoice volume, and edge cases, then build against your actual chart of accounts and tax setup. Typical delivery is one working week from confirmed scope. You get the work validated on a staging bench with UAT before anything touches production, a documented go-live, and a post-go-live support window. There are no fabricated adoption numbers here — just a scoped engagement, a working app, and the source code handed to you.