Construction GST is where generic invoicing tools quietly fail
GST on construction isn't simple invoicing. It's intra-state versus inter-state deciding CGST/SGST or IGST. It's the right SAC code for works contracts. It's Reverse Charge Mechanism on certain supplies. It's tax interacting with retention on a Running Account bill. Get any of it wrong and the invoice is queried, input credit is lost, or a mismatch shows up in reconciliation months later. Generic invoicing tools — built for a shop selling products — don't model any of this.
GST billing software built for contractors bakes these rules in. It applies CGST/SGST or IGST based on place of supply, carries the SAC you've set per work order, handles RCM where relevant, and layers tax correctly on RA bills with retention. The result is a tax invoice that's compliant by construction, so your filing is clean and your credits aren't lost to avoidable errors.
The core idea: the GST logic of a works contract should be built into the bill — not re-decided, and re-risked, on every invoice.
See it in action
Here's a GST tax invoice in True Site Sync — CGST/SGST split, SAC and retention handled.
| Description | SAC | Amount | GST | Total |
|---|---|---|---|---|
| RCC works (RA-4) | 995421 | ₹8,10,000 | 18% | ₹9,55,800 |
| Blockwork & plaster | 995422 | ₹2,92,000 | 18% | ₹3,44,560 |
| Retention held | — | −₹58,000 | — | −₹58,000 |
Illustrative GST tax invoice — SAC, CGST/SGST and retention applied per the works contract.
How compliant GST billing works
Set tax per work order
Configure GST rate, SAC/HSN, place of supply and RCM once on the work order.
Bill from measurements
RA bills and invoices build from measured work, with retention applied automatically.
Tax applied correctly
CGST/SGST or IGST is chosen by place of supply, with the right SAC, on every bill.
Export & file
A GST-compliant tax-invoice PDF, with figures that reconcile to your returns.
GST, the way construction needs it
CGST/SGST vs IGST
Chosen automatically by place of supply — intra vs inter-state.
SAC codes
Correct works-contract SAC per work order, on every invoice.
RCM
Reverse Charge handled where it applies.
Retention + tax
Tax layered correctly on RA bills with retention.
Compliant invoices
Tax invoices that match the portal and your accountant.
Reconciles
Figures that tie back to your GST returns.
Who uses it
Inter-state projects
Bills an out-of-state client with IGST applied automatically and the right SAC, avoiding the classic place-of-supply error.
Tax on running accounts
Raises RA bills where GST and retention interact correctly, so each bill is compliant and the client's QS has nothing to query.
Clean filing
Hands the accountant invoices whose CGST/SGST/IGST and SAC already reconcile, cutting filing corrections and lost credit.
Contractor GST software vs. generic invoicing
| Task | Generic tool | True Site Sync |
|---|---|---|
| CGST/SGST vs IGST | Manual choice | By place of supply |
| Works-contract SAC | Typed each time | Per work order |
| RCM | Not modelled | Handled |
| Tax on RA + retention | Error-prone | Correct |
| From site measurement | No | Yes |
| Works offline on site | — | Yes |
GST is one link in the billing chain
GST billing sits on top of RA billing and construction billing, priced from your BOQ and work orders and flowing into cash flow. Need to check a figure fast? Use the free GST calculator. For the full compliance picture, see Indian construction billing, cash flow & compliance.
GST billing for contractors — FAQs
What is GST billing software for contractors?
It is billing software that applies construction GST rules correctly — CGST/SGST or IGST by place of supply, the right works-contract SAC, RCM where applicable, and tax layered correctly on RA bills with retention — so your tax invoices are compliant and reconcile to your returns.
Does it decide CGST/SGST vs IGST automatically?
Yes. Based on the place of supply set on the work order, it applies CGST/SGST for intra-state and IGST for inter-state billing, removing the most common place-of-supply error.
Does it handle SAC codes and RCM?
Yes. You set the works-contract SAC per work order so it appears correctly on every invoice, and Reverse Charge Mechanism is handled where it applies.
Does it handle GST together with retention on RA bills?
Yes. It applies tax and deducts retention correctly on Running Account bills, so each RA bill is compliant and there is nothing for the client's QS to query.
Does it work offline on site?
Yes. True Site Sync is offline-first — you measure and bill from site with no signal, and it syncs when you reconnect.
How much does it cost?
True Site Sync starts at ₹2,500/year for the Solo plan with a free 7-day trial of the full platform.
We kept getting GST wrong on out-of-state projects — IGST versus CGST/SGST — and losing input credit to mismatches. Now the software picks it by place of supply and puts the right SAC on every bill. Our accountant's filing corrections have basically stopped.
Get construction GST right, every bill
Start free — compliant tax invoices from real measurements.
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