Construction and property

GST invoice format for a waterproofing contractor

A waterproofing contractor's GST invoice should identify the area treated (terrace, basement, bathroom, water tank), measured square metres, the system used such as APP membrane, polyurethane coating or crystalline treatment, and the warranty period offered. Roofing and waterproofing services fall under SAC 995453 and, when chemicals and membranes are supplied, the job is a works contract at 18%. Chemicals sold separately carry their own HSN, for example bitumen under 2713 or waterproofing compounds under 3214 or 3824.

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Sample waterproofing contractor invoice

Description	HSN/SAC	Qty	Rate (₹)	Taxable (₹)	GST
Terrace waterproofing: APP membrane 3 mm torch-applied with primer and protective screed (composite)	995453	260 SQM	620.00	1,61,200.00	18%
Bathroom sunken area waterproofing with polymer-modified cementitious coating, 2 coats	995453	48 SQM	420.00	20,160.00	18%
Removal of existing brickbat coba and disposal	995431	260 SQM	95.00	24,700.00	18%
Bitumen 85/25 for hot application, 25 kg pack (sold separately)	2713	4 NOS	1,850.00	7,400.00	18%
Polyurethane sealant for expansion joints, 600 ml sausage	3214	12 NOS	540.00	6,480.00	18%
Taxable value				₹2,19,940.00
GST (CGST + SGST, or IGST if inter-state)				₹39,589.20
Invoice total				₹2,59,529.20

Sample prices are illustrative. Check the GST rate for your exact item or service before billing.

Extra fields a waterproofing contractor invoice needs

Area treated and location: Terraces, basements, sunken bathrooms and overhead tanks need different systems. Naming the location and measured area on each line lets the client verify that every leaking zone was covered.
Waterproofing system and layers: Clients compare quotes on system rather than price alone. Writing 'APP membrane 3 mm, torch-applied, over primer, with protective screed' shows exactly what was laid.
Warranty period and terms: Waterproofing is sold on guarantee. Printing the warranty years and conditions, such as no later drilling, on the invoice makes it the document the client will use if leakage recurs.
Pond or flood test record: A water-ponding test for 24 to 72 hours proves the system. Quoting the test date on the invoice records that the work was checked before being covered.
Surface preparation: Removing old tiles or brickbat coba, grinding and repairing cracks is substantial work. Billing it separately prevents arguments that it was included in the per-square-metre rate.
Product batch numbers: Chemical manufacturers honour product warranties only with batch details. Recording batch numbers on the invoice supports any later claim against the manufacturer.

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)
Date of issue
Customer name, address and GSTIN (if registered)
Place of supply with state name
HSN/SAC code per item
Description, quantity and unit
Taxable value after discounts
GST rate and CGST + SGST or IGST amounts
Signature or digital signature

GST rules that matter for a waterproofing contractor

Roofing and waterproofing as construction service

The SAC annexure lists 995453, roofing and waterproofing services, under special trade construction services. When you supply membranes, chemicals and labour together, the contract is a works contract because the result becomes part of the building, and it is taxed at 18% on the full value. Even repair-only waterproofing of an old building, where chemicals are applied as part of the job, follows the same treatment because it is repair of immovable property.

Rates on waterproofing materials

Notification 9/2025-Central Tax (Rate) places petroleum bitumen under 2713 and bituminous mixtures under 2715 in Schedule II at 18%. Glaziers' putty, resin cements and mastics under 3214 are at 18%, and plastic sheets and membranes under 3920 or 3921 are also at 18%. If you sell chemicals over the counter from a shop, use these HSN lines; for site jobs the materials are absorbed into the works contract.

Warranty and later repair visits

Many contractors offer five- or ten-year guarantees. A free repair visit under warranty is not a new supply if the warranty was priced into the original contract, and no fresh invoice is needed. If you charge for repairs outside warranty, issue a new tax invoice at 18% under 995453 or the relevant repair code. Keep the original invoice number on warranty visit reports.

Housing societies and common-area work

Terrace waterproofing for a cooperative housing society is a common-area works contract. The society, if registered, cannot claim credit because section 17(5)(c) blocks credit on works contracts for immovable property. Members sometimes ask for separate bills to claim nothing; it is enough to bill the society and mention the managing committee's work order.

E-invoice for large contractors

Waterproofing specialists serving builders and industrial clients may cross the ₹5 crore aggregate turnover limit. From that point every B2B invoice must be reported to the Invoice Registration Portal within the time limits, and an invoice without IRN is not a valid tax invoice for the recipient's credit.

Common billing mistakes

Describing the job only as 'waterproofing work' without area, system and warranty, making a later guarantee claim hard to prove.
Charging separate GST on chemicals at their HSN rate and labour under SAC on a single site contract.
Issuing a fresh tax invoice for a free warranty visit and then not collecting the tax.
Forgetting to bill demolition of old coba separately, leaving it unpaid.
Giving a ten-year guarantee on the invoice while the manufacturer's product warranty runs for only five, leaving the contractor exposed for the gap.
Recording basement and terrace areas in one total, so a later leak in one zone cannot be traced to the system and batch used there.

Waterproofing contractor GST invoice: FAQ

What SAC code is used for waterproofing services?

Use 995453, roofing and waterproofing services. Repair and maintenance of such work can be coded under 995459.

What GST rate applies to waterproofing work?

Waterproofing with materials is a works contract taxed at 18%. Waterproofing chemicals and bitumen sold separately are also at 18% under their HSN.

Can my client claim credit on waterproofing?

Generally no, because section 17(5)(c) blocks credit on works contracts for construction, including repair and renovation capitalised to the building. A builder doing further works contract supply is an exception.

Should the warranty be printed on the GST invoice?

It is not a GST requirement, but printing warranty period and terms makes the invoice the single document a client keeps for future claims.

What HSN applies to waterproofing chemicals?

It depends on the product: bitumen 2713, bituminous mixtures 2715, sealants and putty 3214, and some admixtures under 3824. All of these are taxed at 18%.

Sources: CBIC — Notification 9/2025-Central Tax (Rate), 17 Sep 2025 · ICAI IDTC — Notification 9/2025-Integrated Tax (Rate) as corrected 18 Sep 2025 · CBIC — Scheme of Classification of Services (SAC annexure)

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