A running bill tells your client how much work was done. A tax invoice is the document your client books, pays against and uses for its own GST records. If the invoice is missing a GSTIN, a place of supply or an HSN/SAC code, it comes back, and the payment waits. This guide walks through the fields a GST tax invoice carries, how the tax is shown, and how a certified RA bill becomes an invoice. It covers format only.
Running bill vs tax invoice
On most contracts the RA bill comes first. It is a measurement document: previous, this bill and cumulative quantities, checked and certified by the client’s engineer. Once the client certifies it, you raise a tax invoice for the certified amount. The RA bill shows the work; the invoice is the tax document.
Keep the two linked. Put the RA bill number on the invoice, and the invoice number in your RA bill register, so anyone can trace an invoice back to the measurements behind it.
Fields on a GST tax invoice
GST rules set out the particulars a tax invoice must carry. In general terms, a contractor’s invoice for works should show the following. Your CA can confirm whether anything else applies to your contracts.
| Field | What to write | Common slip |
|---|---|---|
| Document title | "Tax Invoice" | Calling it a "bill" or "estimate" |
| Supplier details | Your name, address and GSTIN | GSTIN from an old letterhead or another branch |
| Invoice number | A unique serial number in a consecutive series for the financial year | Reusing a number after cancelling an invoice |
| Invoice date | The date of issue | Backdating to match the RA bill period |
| Recipient details | Client name, address and GSTIN, where the client is registered | Using the site address instead of the registered one |
| Place of supply | The state, named in words | Leaving it blank or guessing it |
| HSN / SAC | The code for each line, as your CA confirms | One code copied onto every line without checking |
| Description and quantity | Item description, unit and quantity, matching the certified bill | A single line saying "work done as per RA-3" |
| Taxable value | Value of each line after any discount shown | Showing only the total, not per line |
| Rate and tax amount | The tax rate and amount, split as CGST + SGST/UTGST or IGST | Showing both CGST/SGST and IGST on one line |
| Invoice total | Total in figures, and in words | Words and figures that do not match |
| Signature | Signature or digital signature of the supplier or authorised signatory | Unsigned PDFs sent from a personal email |
Run your finance & billing on CivilPilot
Expenses, payment requests, GST invoices, payables and project P&L, kept current by the work itself.
CGST + SGST or IGST: how the split is shown
GST on an invoice appears in one of two ways. When the supplier’s state and the place of supply are the same, the tax is shown as two equal parts, CGST and SGST (or UTGST in a union territory). When they are in different states, the whole tax is shown as IGST. A single line never carries both.
For construction work, deciding the place of supply is not always as simple as reading the client’s address, so treat it as a question for your CA on each new contract. Once it is decided, the split on the invoice follows from it.
GST invoice format in ExcelA tax invoice sheet with every field above, taxable value and CGST/SGST or IGST worked out from the rate you enter, plus an invoice register. Rate cells are left blank for you to fill.Free download · Excel · no sign-upExample: turning RA-3 into a tax invoice
Take the RA-3 bill from our RA bill guide. The client certifies this bill’s quantities: 45 cum of brickwork at ₹6,500 and 600 sqm of plaster at ₹320. Quantities and rates are sample figures for illustration only. The invoice lines look like this:
| Line | HSN / SAC | Qty | Rate | Taxable value | GST rate | Tax |
|---|---|---|---|---|---|---|
| Brickwork 230 mm (RA-3) | As per CA | 45 cum | 6,500 | 2,92,500 | __ % | Taxable value × rate |
| Internal plaster 12 mm (RA-3) | As per CA | 600 sqm | 320 | 1,92,000 | __ % | Taxable value × rate |
| Total | 4,84,500 |
Tax is the taxable value multiplied by the rate, then shown either as CGST + SGST in two equal halves or as IGST in full, depending on the place of supply. This guide deliberately gives no rate. How deductions on the RA bill, such as retention or advance recovery, are treated on the invoice is also a question for your CA, so agree it once per contract and follow it on every bill. Our guide to retention money in construction explains how retention is tracked.
Step by step: from certified bill to sent invoice
- 1Get the RA bill certified, with the certified quantities in writing.
- 2Copy item, unit, quantity and rate from the certified bill. Do not retype rates from memory.
- 3Enter the HSN/SAC code and rate confirmed by your CA for each line.
- 4Fill the place of supply and choose CGST + SGST or IGST accordingly.
- 5Take the next number in your invoice series and date the invoice the day you issue it.
- 6Check the total in words, sign it, and send it with a copy of the certified bill.
- 7Record the invoice in your register and follow up the payment against it.
What to send with the invoice
Clients pay faster when the invoice arrives with everything their accounts team needs to check it. A simple covering set is:
| Document | Why it helps |
|---|---|
| Signed tax invoice | The document the client books and pays against |
| Certified RA bill | Shows the quantities behind every invoice line |
| Measurement sheets | Evidence for any quantity that is questioned |
| Work order or contract reference | Ties the rates to an agreed document |
| Bank details on your letterhead | Avoids a separate round of emails before payment |
Send it to the person named in the contract for billing, and keep a dated record of when it was sent. That date matters when you follow up.
Common GST invoice mistakes
- Gaps or repeats in the invoice series. A deleted draft that burned a number, or two people issuing from separate sheets.
- Wrong recipient GSTIN. The client’s other branch or an old registration.
- Place of supply left blank. It drives the CGST/SGST vs IGST split, so it cannot be skipped.
- Lump-sum description. "Work done as per RA bill" makes the invoice hard to check against the measurements.
- Editing an issued invoice. Once sent, correct it the way your CA advises instead of quietly changing the file.
An invoice is only as clean as the agreement behind it. If items, units and rates are fixed in the work order, the invoice becomes a matter of copying certified quantities.
Do this in CivilPilot
In CivilPilot’s finance and billing, you create GST or non-GST invoices against a project or a CRM lead. A GST invoice carries your GSTIN, the client’s name, address and GSTIN, place of supply, and HSN/SAC, quantity, unit, rate, discount and a tax rate you enter on each line. CivilPilot works out the taxable value and shows the tax as CGST + SGST when the client’s state code matches the state in your GSTIN, and as IGST otherwise. It will not issue a GST invoice without your GSTIN, a place of supply and an HSN/SAC code on every line.
Drafts stay editable and take no number. The invoice number is given only when you issue it, from a separate series for GST and non-GST invoices in each financial year, so a deleted draft never leaves a gap. You can download the invoice as a PDF with the amount in words, cancel an issued invoice with a reason instead of deleting it, and record receipts against it. CivilPilot does not decide tax rates, SAC codes or place of supply, and it does not create an invoice from an RA bill automatically; you enter the certified lines yourself. It works in a phone browser.
