If you sell across US states from ERPNext, native tax handling runs out of road fast. ERPNext's Sales Taxes and Charges Template and Tax Rule DocTypes were designed for relatively static, jurisdiction-per-template tax setups, not the 11,000+ US rate jurisdictions where sourcing rules, product taxability, and rooftop-accurate rates change by ship-to address and change often. Teams end up maintaining hand-built rate tables, guessing at economic-nexus thresholds state by state, and reconciling what ERPNext charged against what they actually owe at filing time. That gap is where over-collection, under-collection, and audit exposure live.

ECOSIRE builds the erpnext-taxjar-connector as a proper Frappe app (its own module, DocTypes, and hooks.py wiring) that makes TaxJar the calculation and reporting engine behind ERPNext. On validation of a Sales Invoice, POS Invoice, Sales Order, or Quotation, a doc_events handler calls TaxJar's /v2/taxes endpoint with the customer's ship-to address and line items — resolving product taxability via TaxJar product tax codes mapped onto ERPNext Item (or Item Group) — and writes the returned jurisdiction breakdown back into the Sales Taxes and Charges child table so your GL and printed documents stay the single source of truth. Rates are cached and calls are idempotent so a re-validate or amend doesn't double-fire.

On the reporting side, a scheduler event pushes committed transactions to TaxJar via /v2/transactions/orders and syncs refunds/credit notes as /v2/transactions/refunds, giving you filing-ready, multi-channel consolidated data (ERPNext plus any marketplace transactions you already feed TaxJar). A dedicated TaxJar Nexus State DocType and a background job track your economic-nexus exposure against each state's threshold and surface an alert before you cross it, so registering is a decision and not a surprise. Tax-exempt customers are handled through TaxJar exemption certificates keyed to the ERPNext Customer, and every API request/response is logged to a TaxJar Sync Log DocType for audit and troubleshooting. Configuration lives in a single TaxJar Settings DocType (API token stored encrypted, sandbox/production toggle), gated by a role profile so only your finance admins can change it, and whitelisted methods expose recalculate/backfill actions to authorized users and the REST API.

Because this is built to order, we start from your real setup — the states you sell into, your item catalog and taxability, your channels, and whether you're on Frappe/ERPNext v15 or v16 — and deliver against confirmed scope. Typical delivery is 2-4 weeks once scope is locked. You get the installable app source for your version, a UAT pass on a staging bench with a rollback plan, install and configuration on your environment, documentation, a training session, and a post-go-live support window. It targets Frappe/ERPNext v15 and v16 and is handed over as a git repository you own.