GST invoice format for a structural steel fabrication and erection contractor
An on-site steel fabrication and erection contractor bills by tonnage: fabricated and erected weight of columns, rafters, purlins and bracing. The invoice should give the drawing or erection mark numbers, the weight basis (theoretical or weighbridge), and whether steel was supplied by you or by the client. Erection with material is a works contract at 18% under SAC 995455, while fabricated structures supplied ex-works fall under HSN 7308, also at 18%.
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Sample structural steel fabrication and erection contractor invoice
Description
HSN/SAC
Qty
Rate (₹)
Taxable (₹)
GST
Fabrication and erection of structural steel shed incl. steel, bolts and primer (composite)
995455
18.5 TON
92,000.00
17,02,000.00
18%
Erection only of client-supplied steel members incl. tools and tackles
995455
6 TON
14,000.00
84,000.00
18%
Fabricated MS roof truss, ex-works supply
7308
2400 KGS
88.00
2,11,200.00
18%
HSFG bolts M20 with nut and washer
7318
400 NOS
42.00
16,800.00
18%
Taxable value
₹20,14,000.00
GST (CGST + SGST, or IGST if inter-state)
₹3,62,520.00
Invoice total
₹23,76,520.00
Sample prices are illustrative. Check the GST rate for your exact item or service before billing.
Extra fields a structural steel fabrication and erection contractor invoice needs
Drawing and erection mark numbers
Pre-engineered and conventional steel buildings are detailed member by member. Listing erection marks or drawing numbers lets the client's engineer tie each tonne to an approved drawing.
Weight basis
Clients and contractors argue over theoretical versus actual weight. Stating whether tonnage is from section tables or weighbridge slips, with slip numbers, avoids disputes on every bill.
Steel source: own or client-supplied
Many factory owners buy steel and pay only fabrication and erection. A clear line on whose steel was used decides the taxable value and the scope of the works contract.
Wastage and scrap adjustment
Client-supplied steel creates offcuts. Showing allowable wastage and how scrap is returned or credited explains material reconciliation at the final bill.
Painting and surface preparation
Primer, intermediate and finish coats, or galvanising, add to cost. Listing the protective system and its DFT makes the scope explicit.
Crane and equipment
Erection often needs a hydra or crawler crane. Showing crane days or hire charges separately helps the client see the cost of heavy lifts.
Standard GST invoice fields
Rule 46 of the CGST Rules applies to every tax invoice, including this one:
✓Supplier name, address and GSTIN
✓Consecutive invoice number (max 16 characters, unique for the year)
GST rules that matter for a structural steel fabrication and erection contractor
Works contract or supply of fabricated structures
When you fabricate steel and erect it on the client's site so that it becomes part of a building, the contract is a works contract under SAC 995455, structural steel erection services, taxed at 18%. If you only fabricate in your workshop and deliver structures that the client erects, you are supplying goods under HSN 7308, structures and parts of structures of iron or steel, which Notification 9/2025 places at 18%. Prefabricated buildings as a whole fall under 9406, also at 18%.
Client-supplied steel and job work
When the client supplies steel and you only fabricate it in your workshop and return it, the activity may be job work on the client's goods. Job work services generally attract 18%, but the client must send steel under a delivery challan and track it under section 143. Where you fabricate and also erect on site, the combined service is a works contract on your labour and consumables, without adding the client's steel value.
Weighbridge slips and e-way bills
Fabricated members moving from your shop to the site are goods in transit. If you are supplying them as goods, the tax invoice and an e-way bill above ₹50,000 travel with the truck. If they move under your own works contract, use a delivery challan and still generate an e-way bill on value. Keep weighbridge slip numbers on the invoice to support quantities.
Input tax credit on steel and consumables
Steel bars, angles and sections under chapter 72, bolts under 7318 and paints all carry 18%. As a works contractor, you can claim credit on these because section 17(5)(c) permits credit where the input is used for further supply of works contract service. Ensure supplier invoices show your GSTIN and the site or workshop address, or credit can be questioned.
TDS and retention on industrial projects
Industrial clients often deduct income tax TDS under section 194C and hold retention until the structure passes load tests. GST is due on the full invoice value irrespective of these deductions. Track retention so that the final bill clearly releases it without raising fresh GST.
Common billing mistakes
✕Adding the value of client-supplied steel to the taxable value of an erection-only invoice.
✕Billing ex-works fabricated structures under a construction SAC instead of HSN 7308.
✕Using theoretical weights on one bill and weighbridge weights on another, causing tonnage disputes.
✕Moving fabricated members without an e-way bill because 'it is our own job'.
✕Booking crane hire invoices that show the client's GSTIN instead of yours, so the credit never appears in your GSTR-2B and the erection margin quietly shrinks.
Structural steel fabrication and erection contractor GST invoice: FAQ
What SAC code applies to steel erection?
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Structural steel erection services are coded 995455. Fabrication with erection under one contract is a works contract billed under this code at 18%.
What is the HSN for fabricated steel structures?
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Structures and parts of structures of iron or steel, such as trusses, columns and roofing frameworks, fall under HSN 7308 at 18%. Prefabricated buildings are under 9406.
Is GST charged on client-supplied steel?
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No. If the client supplies steel free of cost and it is not part of your consideration, you charge GST only on your fabrication and erection charges.
Can a factory owner claim credit on my steel shed invoice?
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Credit for works contracts and goods used to construct immovable property on own account is blocked under section 17(5), except for plant and machinery. Factory sheds are generally treated as buildings, so credit is usually not available.
How should weight be shown on the invoice?
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State whether the tonnage is theoretical or actual, and list the weighbridge slip numbers if actual. Use the same basis throughout the contract, and attach the member-wise weight schedule as an annexure for the client's engineer.