ERPNext for Auto Ancillary Manufacturers India —
BOM, Subcontracting & ITC-04 Guide

Why Tamil Nadu is India's Auto Ancillary Heartland — and Why ERP Gets Harder Here

Tamil Nadu accounts for roughly 35% of India's automobile production and an even larger share of auto ancillary output. The corridor from Chennai to Hosur and down to Coimbatore is home to Tier-1 and Tier-2 suppliers for Hyundai, Ford (legacy plants), TVS, Royal Enfield, Ashok Leyland, and dozens of international OEMs that have set up procurement hubs in the region.

Trichy, Madurai, and the surrounding districts form a dense ecosystem of precision machining, casting, forging, and rubber moulding companies supplying this corridor. These are not simple assembly operations. They run:

• Multi-level sub-assemblies — a brake assembly has 12 components; each component has its own BOM with 3–8 raw materials; raw materials have alternate vendors with different lead times.
• Job work (subcontracting) at multiple tiers — heat treatment goes to vendor A, plating to vendor B, the semi-finished part comes back, gets assembled and goes to vendor C for testing before final dispatch.
• GST ITC-04 compliance — every challan for goods sent to a job worker must be tracked, reported quarterly on ITC-04, and reconciled. A mid-size plant sends 300–500 challans a month. Doing this in Excel is a compliance disaster.
• Customer-specific drawing revisions — OEM sends a drawing rev from B to C. Every open work order, every BOM, every quality checkpoint has to reflect the new revision. One missed rev causes a rejection and a costly customer audit.
• IATF 16949 and AS9100 traceability — full lot traceability from incoming raw material heat number to final part serial number, with full genealogy for field failures.

No Excel sheet handles all five. Most SME-level ERPs handle two or three but not in an integrated way. ERPNext handles all five — and PS Digitise has implemented it specifically for South India auto ancillary plants.

Multi-Level Bill of Materials (BOM) in ERPNext

A Bill of Materials in ERPNext is not just a flat component list. It supports multi-level BOM explosion — each sub-assembly has its own BOM, and ERPNext resolves the full material requirement tree when you create a production plan or work order.

How Multi-Level BOM Works in ERPNext

Consider a brake calliper assembly. The finished part (Level 0) has 4 sub-components (Level 1). Two of those sub-components are themselves manufactured in-house from raw materials (Level 2). One is subcontracted — sent to a job worker as a semi-finished part (Level 2 with subcontracting). The raw materials at Level 2 are sourced from 2–3 alternate vendors with different lead times.

In ERPNext, you define each BOM at its own level and link them. When you create a Work Order for the finished calliper, ERPNext:

• Explodes the full multi-level BOM automatically
• Calculates raw material requirements at every level
• Creates purchase requests for items below reorder level
• Creates sub-work orders for in-house sub-assemblies
• Creates Subcontracting Orders for job work items
• Tracks WIP inventory at each level separately

BOM Scrap and By-Product Handling

Auto ancillary manufacturing generates significant scrap — metal swarf from machining, rubber flash, casting gates and risers. ERPNext BOM supports:

• Scrap items with expected percentage yield — actual vs expected scrap variance is tracked
• By-products with their own valuation — returned to inventory and valued at standard cost
• Operation-level scrap — scrap generated at each workstation, not just at the BOM level

Drawing Revision Control — Customer-Specific BOMs

In auto ancillary, the same physical part may have different specifications for different OEM customers. Customer A (Hyundai) specifies surface roughness Ra 1.6; Customer B (Ashok Leyland) specifies Ra 3.2. Same machining process, different quality checkpoint.

ERPNext handles this with customer-specific BOMs linked to the Sales Order. When a Work Order is created from a customer Sales Order, it pulls the BOM specific to that customer. Quality Inspection templates are attached to the customer BOM — so the inspector sees the correct tolerance spec for each customer, on every job.

Subcontracting in ERPNext — The Job Work Workflow

Subcontracting (job work) is central to auto ancillary manufacturing. Heat treatment, phosphating, zinc plating, powder coating, calibration — most plants outsource one or more operations because the investment in in-house equipment is not justified by volume. ERPNext has a dedicated Subcontracting module that handles the entire job work flow.

The Complete Subcontracting Flow in ERPNext

Each step creates a document trail in ERPNext. The system tracks:

• Quantity sent vs quantity received — auto-calculates outstanding at vendor
• Days at vendor — overdue job work alerts when parts exceed stipulated turnaround time
• Raw material supplied to vendor — if you supply the raw material and pay only for service, ERPNext tracks the material on your books as "material with vendor" — it does not leave your inventory valuation
• Vendor-wise subcontracting cost — actual cost per operation per vendor for rate negotiation
• Multi-hop job work — send to Vendor A, receive back, send semi-finished to Vendor B

Quality Inspection at Inward from Subcontractor

ERPNext triggers a Quality Inspection automatically on every Subcontracting Receipt if configured to do so. The inspector sees the inspection template, records measurements, and approves or rejects. Rejected lots generate a Non-Conformance Report (NCR) linked to the vendor and the batch — directly feeding your vendor quality scorecard.

ITC-04 Compliance in ERPNext — Challan Tracking for Job Work

ITC-04 is the GST form that every manufacturer sending goods to a job worker must file quarterly. It reports:

• Goods sent to job workers (Table 4A)
• Goods received back from job workers after processing (Table 4B)
• Goods directly supplied from job worker's premises to customer (Table 4C)

A mid-size auto ancillary plant sending components to 5–10 job workers may generate 300–600 challans per quarter. Reconciling these manually in Excel is not just tedious — it is a significant compliance risk. Missing challans, wrong GSTIN, wrong HSN code on the challan: each is a potential GST notice.

How ERPNext Handles ITC-04

When you create a Stock Entry to send goods to a subcontractor in ERPNext, the system:

• Generates a job work challan with the correct fields for ITC-04 reporting — challan number, date, GSTIN of job worker, HSN code, quantity and taxable value
• Tracks the challan date — and flags challans approaching the 1-year / 3-year limit
• On receipt back (Subcontracting Receipt), marks the challan as closed — so outstanding challans are always visible
• Generates ITC-04 report data — the export from ERPNext maps directly to the ITC-04 form fields: Table 4A, 4B, and 4C

Your CA or GST consultant uploads the ERPNext export to the GST portal. No manual reconciliation. No missed challans. Full audit trail.

IATF 16949 & AS9100 Traceability in ERPNext

IATF 16949 (automotive) and AS9100 (aerospace) both require full lot traceability — the ability to trace a finished part forward to the customer and backward to the raw material, with every operation, inspection, and rework event in between. This is called the part genealogy.

In a field failure or recall scenario, the OEM sends you a part number and a manufacturing date range. You must identify every batch produced in that range, which customers received those batches, and what raw material heat numbers were used — all within hours, not days.

How ERPNext Enables IATF Traceability

• Batch numbers on every incoming raw material lot — heat number, supplier lot number, test certificate number
• Serial numbers on finished parts where customer requires serial-level traceability
• Work Order lot tracking — which raw material batches were consumed in which Work Order
• Quality Inspection records linked to every batch at every operation (incoming, in-process, final)
• Rework and scrap recording at operation level — NCR linked to the specific batch and operation
• Delivery Note to Sales Order to Work Order to raw material — full forward and backward trace in one click

Control Plan and PFMEA Documentation

ERPNext does not generate Control Plans or PFMEAs natively — these are Word/Excel documents maintained separately by quality teams. However, ERPNext integrates with these documents by linking Quality Inspection templates to the control plan characteristics:

• Each quality checkpoint in the ERPNext inspection template corresponds to a row in the control plan
• Measurement values recorded in ERPNext are automatically compared to control limits (USL/LSL)
• Out-of-control points trigger an NCR — which can be linked to the corresponding PFMEA risk
• Statistical summaries (Cpk, trend charts) can be exported for SPC analysis

Case Study — Precision Sheet Metal Manufacturer, Chennai

ERPNext vs Alternatives for Auto Ancillary — Feature Comparison

PS Digitise ERPNext Implementation for Auto Ancillary — What's Included

PS Digitise has developed a fixed-scope, fixed-price ERPNext package specifically for auto ancillary manufacturers in Tamil Nadu and South India. It is not a generic ERPNext implementation — every module and workflow is pre-configured for the auto manufacturing context.

What's Included in the Auto Ancillary Package

• Multi-level BOM setup for up to 50 finished goods (5-level BOM support)
• Work Order and Job Card setup with workstation routing (machining, grinding, inspection)
• Subcontracting module for up to 10 job workers — challan flow, ITC-04 ready
• Quality Inspection templates — incoming (raw material), in-process, final inspection
• Batch and serial number traceability — IATF-compliant genealogy report
• Customer-specific BOM versions with drawing revision control
• GST compliance — e-Invoice, e-Way Bill, ITC-04 data export
• Production Planning module — MRP-based purchase requisitions from forecast
• Vendor Quality scorecard — rejection rate, NCR tracking per vendor
• User training — 3 sessions (production team, quality team, accounts team)
• Go-live support — 4 weeks on-site / remote handholding

What's Not Included (Separate Scope)

• Payroll / HR — handled by Frappe HRMS (separate quote)
• Legacy data migration from Tally — quoted separately based on data volume
• Custom reports beyond standard package — additional per-report fee
• IATF documentation (Control Plans, PFMEAs) — these are your documents; ERPNext hosts the data but does not generate IATF document templates

Implementation Timeline

Is ERPNext Right for Your Auto Ancillary Plant?

ERPNext is the right fit if you are:

• A Tier-2 or Tier-3 auto ancillary manufacturer with 20–500 employees
• Running multi-level BOMs with 3 or more levels of sub-assembly
• Sending goods to 2 or more job workers regularly
• Filing ITC-04 quarterly and doing it manually in Excel
• Pursuing or maintaining IATF 16949 / AS9100 certification
• Receiving customer-specific drawing revisions and struggling to track them
• Based in Tamil Nadu, Andhra Pradesh, Karnataka, or Kerala — South India focus
• Looking for a system that costs ₹0 in software licensing

ERPNext may not be the right fit if you are:

• A large Tier-1 with 1,000+ employees and existing SAP investment — SAP migration is rarely justified
• A purely trading company with no manufacturing — simpler ERP options exist
• A startup with fewer than 10 employees — even Excel may suffice initially
• Needing MES (Manufacturing Execution System) with machine-level IoT integration — ERPNext is not a real-time MES

Frequently Asked Questions