---
title: Metal fabrication job-work ERP: Section 143 challans, sheet scrap, and heat numbers
canonical: https://naffo.tech/blog/metal-fabrication-job-work-challan-scrap-traceability
question: How does an engineering and metal fabrication workshop manage GST Section 143 job-work challans and off-cut scrap?
published: 2026-11-15
updated: 2026-11-15
author: Naffo Heavy Engineering Desk (Fabrication management, subcontracting controls, and precision engineering ERP)
reviewed_by: Harsh Patel (Head of ERP Architecture at Naffo)
publisher: naffo.tech — https://naffo.tech
category: Engineering & Fabrication
tags: metal fabrication ERP, job-work delivery challan GST, Section 143 job-work compliance, steel plate nesting scrap ERP, heat number traceability manufacturing, sheet metal costing software
reading_time_minutes: 6
license: Free to quote with attribution to naffo.tech (https://naffo.tech/blog/metal-fabrication-job-work-challan-scrap-traceability)
---

# Metal fabrication job-work ERP: Section 143 challans, sheet scrap, and heat numbers

**Question:** How does an engineering and metal fabrication workshop manage GST Section 143 job-work challans and off-cut scrap?

**Answer:** Metal fabrication and engineering workshops manage job-work by issuing statutory GST Section 143 delivery challans with strict tracking of material weight sent versus finished components and process scrap returned within statutory time limits. High-precision fabrication requires maintaining mill heat number traceability from raw steel plates to laser-cut profiles, dynamic nesting software yield reconciliation, and inventory valuation that distinguishes reusable plate off-cuts from non-usable melt scrap.

Naffo is independently developed. Tally and TallyPrime are trademarks of Tally Solutions Pvt. Ltd. Other company and product names belong to their respective owners and are used to identify products or describe compatibility. References do not imply affiliation, endorsement or certification. Integration availability depends on the product version, plan, permissions and configuration; confirm your required workflow before purchase.

## Key takeaways

- Subcontracted job-work must return within 1 year for inputs and 3 years for capital goods under GST Section 143, or it is treated as a deemed tax supply.
- Delivery challans must specify HSN code, input weight, expected output component weight, and acceptable process scrap percentage.
- Steel sheet off-cuts with usable surface area must be re-inwarded to stock at plate cost rather than scrap melt value.
- Raw material mill test certificates (MTC) and heat numbers must follow parts through laser cutting, bending, welding, and powder coating.

## Key figures

- **14%–26%** — Average nesting skeleton scrap in sheet metal laser cutting (Basis: Operational benchmarks across 30 CNC laser cutting workshops processing MS, SS, and Aluminum plates in Pune and Peenya.)
- **3%–5.5%** — Subcontracted job-work material loss without weight-based reconciliation (Basis: Discrepancies identified during job-work reconciliation audits between prime steel issued and returned parts.)

> **The twin challenges of modern metal fabrication**
>
> Metal fabricators face two relentless operational drains: losing valuable sheet metal in unrecorded off-cuts and losing GST compliance control over subcontracted job-work. Under Indian GST law, sending steel sheets out for galvanizing, electroplating, or machining without rigorous Section 143 tracking can trigger deemed sales with 18% GST plus 18% annual interest.

## GST Section 143 job-work compliance: avoiding the deemed supply trap

Under Section 143 of the CGST Act, a principal manufacturer can dispatch capital goods or input materials to a job-worker without paying GST, provided the transaction is covered by a valid **Delivery Challan** (FORM GST ITC-04).

- **Strict Statutory Return Period**: Raw materials and inputs must return to the principal's factory within **one year** from the date of dispatch. Capital goods (such as dies or fixtures) have a **three-year** return limit.
- **The Deemed Supply Penalty**: If goods do not return within 365 days, the law deems the original dispatch as a taxable sale on the very day the delivery challan was issued. The manufacturer must pay GST, plus 18% annual interest from day one.
- **Scrap Accounting**: Any process scrap generated at the job-worker's premises must either be returned to the principal or sold directly by the job-worker with GST paid.

naffo.tech provides an automated aging tracker for all open Section 143 delivery challans. At 60, 90, and 300 days, the ERP alerts procurement managers of outstanding job-worker inventory, preventing accidental deemed-supply tax liabilities.

## Off-cuts vs skeleton scrap: stopping prime steel margin leakage

When a CNC laser cutter nests brackets onto a 2,500 mm × 1,250 mm × 6 mm mild steel plate, the plate rarely gets 100% utilized. In typical production runs, nesting software achieves **78% to 85% material utilization**.

The remaining 15% to 22% of sheet metal falls into two completely distinct commercial categories:

_Distinguishing plate remnants from melting scrap in metal inventory_
| Scrap Category | Physical Form | Commercial Valuation | ERP Handling |
| --- | --- | --- | --- |
| Skeleton Scrap (Melt Scrap) | Thin webs, piercing holes, internal cutouts | Scrap melting rate (₹32/kg vs ₹68/kg prime) | Weighed into scrap bin, credited to job card as scrap recovery |
| Usable Off-Cut (Plate Remnant) | Large un-cut rectangular sections (> 500mm × 500mm) | Prime steel valuation (₹68/kg) | Re-inwarded to inventory as off-cut parent stock with specific dimensions |

When a workshop throws usable off-cuts into the scrap pile or lets them lean against the factory wall without logging them in the ERP, thousands of kilograms of prime steel get sold to scrap dealers for half their value. In naffo.tech, when a laser job card closes, the operator records the remnant plate dimensions, generating a trackable child inventory item.

## Heat number and Mill Test Certificate (MTC) traceability

In pressure vessel fabrication, structural steel frames, and defense contracting, parts cannot be shipped without complete material traceability. Inspectors demand to know the exact steel mill, ladle chemistry, and tensile yield strength of the raw plate used for every bracket.

1. **Plate Inward & MTC Verification** — When steel coils or plates arrive from Tata Steel, JSW, or Jindal, the heat number stamped on the plate edge is entered into naffo.tech alongside the scanned Mill Test Certificate PDF.
2. **Laser Nesting Job Assignment** — The production supervisor selects specific heat numbers for critical customer jobs. The ERP links the work order number to the plate heat code.
3. **Part Marking & Hard Stamping** — Parts cut on the laser carry etched or hard-stamped component part numbers and heat abbreviations.
4. **Final Inspection Dossier Generation** — When generating the final inspection report and dispatch invoice in naffo.tech, the software compiles the complete heat certificate trail with a single click.

## Worked costing example: heavy industrial conveyor bracket

Let us examine the complete production cost for a batch of 50 heavy duty brackets manufactured from 10 mm IS 2062 E250 structural steel plate:

_Full engineering costing breakdown for 50 fabricated brackets_
| Cost Element | Engineering Quantity | Unit Rate | Total Cost for Batch |
| --- | --- | --- | --- |
| Raw Steel Plate (10mm MS) | 420 kg issued (based on nesting layout) | ₹68.00 / kg | ₹28,560.00 |
| Usable Remnant Off-Cut Credit | (-) 65 kg (800mm × 650mm remnant returned to rack) | (-) ₹68.00 / kg (credited at full plate cost) | (-) ₹4,420.00 |
| Skeleton Laser Scrap Credit | (-) 45 kg web scrap collected in tray | (-) ₹32.00 / kg (scrap melt rate) | (-) ₹1,440.00 |
| CNC Fiber Laser Cutting (MHR) | 1.85 machine hours (including pierce cycles) | ₹1,800.00 / laser hour | ₹3,330.00 |
| CNC Hydraulic Press Brake Bending | 3 bends per bracket = 150 bends (0.75 hrs) | ₹650.00 / press hour | ₹487.50 |
| Subcontracted Hot-Dip Galvanizing | Finished component weight: 310 kg sent under Sec 143 challan | ₹24.00 / kg galvanizing charge | ₹7,440.00 |
| Inward/Outward Freight to Job-Worker | Transport van to galvanizing plant | Flat trip charge | ₹850.00 |
| Total Fabricated Batch Cost | Net Output: 50 Galvanized Brackets | Cost per Bracket: ₹696.15 | ₹34,807.50 |

By separating the **₹4,420 off-cut credit** from the **₹1,440 melting scrap credit**, the company costs each bracket at **₹696.15** instead of ₹784.55. This accurate baseline allows the sales engineering team to win competitive tenders while maintaining healthy profit margins.

## Reconciling job-worker material weight and process losses

When dispatching metal parts for external heat treatment, zinc plating, or machining, how do you verify that the subcontractor didn't misplace your parts or dilute chemical baths? In conventional workshops, parts return with rough delivery slips showing only part counts.

In naffo.tech, job-work receiving slips require dual verification: **part count** and **total gross weight**. If parts return from zinc plating with 3% less weight than expected, the software highlights the variance before the invoice is approved for payment.

## Managing tooling, dies, and fixtures sent to vendors

Engineering fabricators frequently send specialized bending dies, punch tooling, or welding fixtures to subcontracting machine shops. Unlike raw materials, these tools are capital assets and must not be consumed as production expenses.

> **Best practice for tool loan management**
>
> Issue tools under a dedicated 'Capital Goods for Job-Work' challan category in naffo.tech.
>
> Track tool location and vendor custody in real time across your vendor ledger.
>
> Ensure tooling returns within the statutory 3-year GST window or is transferred to a fresh maintenance challan.

## Frequently asked questions

### How does naffo.tech handle GST Section 143 delivery challans for job-work?

naffo.tech generates complete GST-compliant Delivery Challans containing HSN codes, weight, description, and job-worker GSTIN. It maintains a real-time aging register that tracks days elapsed against the 1-year input and 3-year capital goods return deadlines, alerting managers before materials cross statutory thresholds.

### Can the software distinguish between reusable plate off-cuts and melting scrap?

Yes. When completing a cutting job card in naffo.tech, operators can record both skeletal scrap (valued at melting scrap rates) and dimensioned off-cuts (re-entered into sheet inventory at prime material cost), preventing prime steel remnants from being written off as scrap.

### How is heat number and mill test certificate traceability maintained through multiple production stages?

Raw material heat numbers are captured during gate receipt and linked to plate inventory batches. When a production work order is created, the heat number flows automatically through laser cutting, bending, and assembly records, allowing you to generate an auditable MTC dossier with a single click.

## Related articles

- https://naffo.tech/blog/dynamic-by-product-costing-scrap-allocation-bom
- https://naffo.tech/blog/purchase-order-vs-goods-receipt-three-way-matching
- https://naffo.tech/blog/fifo-vs-weighted-average-costing-inventory-valuation

---

Published by naffo.tech, an all-in-one business management and manufacturing ERP platform for Indian SMEs — GST compliance, invoicing, inventory, batch manufacturing, yield and wastage control, and double-entry accounting in one system. https://naffo.tech

Markdown source: https://naffo.tech/blog/metal-fabrication-job-work-challan-scrap-traceability/markdown