Bangladeshi finance teams running ERPNext hit the same wall every month: the National Board of Revenue (NBR) expects VAT documents in prescribed Mushak formats — the Mushak 6.3 tax challan (challanpatra), the Mushak 9.1 VAT return, purchase and sales registers, and withholding (VDS) certificates — and stock ERPNext knows nothing about any of them. Out of the box you get generic Sales Taxes and Charges templates and a plain Sales Invoice print format; you do not get an NBR-numbered 6.3 challan, you do not get a return that ties output and input VAT to the return period, and you certainly do not get the Bangla/English bilingual layout the VAT circle expects. Teams paper over the gap with parallel Excel workbooks, manual re-keying, and hand-drawn print formats that drift out of compliance whenever a circular changes.

ECOSIRE builds a dedicated Frappe app — a proper installable app with its own module, not a pile of loose customizations — that makes ERPNext speak NBR VAT natively. We add DocTypes for the Mushak 6.3 challan and the Mushak 9.1 return, each with the fields, child tables, and NBR reference numbering the format requires, plus VAT/SD (supplementary duty) tax templates wired to your chart of accounts and item tax categories. Document generation is driven by hooks.py doc events (on_submit, on_cancel, validate) so that submitting a Sales Invoice can create or update the corresponding 6.3 challan automatically, and a naming series keeps challan numbers gapless and auditable. Bilingual print formats render the same invoice in Bangla and English from one submitted record, and withholding-VAT logic captures deducted VAT at source with the certificate output your suppliers and the VAT authority need.

Under the hood the app uses the patterns a senior Frappe engineer would expect: server scripts and Python controller methods for the tax and rounding math, client scripts for in-form validation and field automation, whitelisted methods exposed over the Frappe REST API so a POS or external billing system can post transactions and pull challan data, and Query Reports (with optional Report Builder views) for the Mushak 9.1 return, sales register, and purchase register filtered by return period. Role profiles and permission rules scope who can raise, submit, and cancel VAT documents; scheduler events can assemble period-end return figures and flag mismatches between output VAT booked and challans issued before you file. Everything targets ERPNext and Frappe v15 and v16 and is delivered as versioned source you own.

Because this is build-to-order, nothing ships until we agree on scope. We start with a short scoping call to confirm your NBR return cadence, VAT/SD rates, VDS scenarios, and which documents you actually file, then build against your requirements, run UAT on a staging bench, and install on your production bench with a rollback plan. Typical delivery is 2-4 weeks from confirmed scope. You receive the Git repository, installable source, technical and user documentation, a training session, and a post-go-live support window — so your finance officer owns a compliant, maintainable ERPNext, not a black box.