How to Make a GST Invoice Online: Fields, Format and Checklist

Sending a clear, correct invoice is the fastest way to get paid. Yet many small businesses and freelancers in India still type bills in a word processor, copy last month's file, and forget to change the invoice number or the tax split. A wrong GSTIN, a missing place of supply or a CGST/SGST split on an inter-state sale can delay payment and create headaches when your customer claims input tax credit.

This guide walks you through making a GST invoice online, step by step: what to collect before you start, which fields to fill, how to choose between CGST + SGST and IGST, how to write the total in words, and the mistakes to check for before you hit send. You can follow along with the Quotation/Invoice Generator on Doffl.

What a GST invoice is (and when you need one)

A tax invoice is the document a GST-registered business issues when it supplies taxable goods or services. It is proof of the sale for you and the basis on which your registered customer claims input tax credit. That is why the details have to be exact.

A few related documents are easy to confuse:

• Quotation (estimate): an offer sent before the work, listing items and prices. It is not a demand for payment.
• Tax invoice: issued for the actual supply, with GST shown.
• Bill of supply: used in some cases where GST is not charged on the invoice, for example by composition taxpayers or for exempt supplies.
• Receipt: confirms that money was received.

If you are not registered under GST, you can still send a simple invoice or bill, but you should not show GST on it. When in doubt about which document applies to you, check the latest rules on the official GST portal or ask your CA.

Step 1: Collect the details before you open the tool

Having everything ready keeps the process to a few minutes. Gather:

1. Your business details: legal name, trade name (if any), full address, GSTIN, phone, email and logo.
2. Customer details: name, billing address, shipping address if different, and their GSTIN if they are registered.
3. Items or services: a clear description, HSN code (goods) or SAC code (services), quantity, unit (pcs, kg, hours) and rate per unit.
4. Tax rate for each line: the GST rate that applies to that HSN/SAC. Rates change from time to time, so confirm the current rate on the official GST rate finder.
5. Payment terms: due date, bank details or UPI ID, and any late-payment note.

Tip: keep a small sheet of your regular items with their HSN/SAC and rate. It saves time and avoids typos every month.

Step 2: Fill in the header fields correctly

The top of the invoice is where most errors happen. In the invoice generator, fill these in order:

• Invoice number: use a consecutive series that is unique for the financial year, such as INV/2026-27/0045. Do not reuse or skip numbers casually. Keep the series short and simple.
• Invoice date: the date you issue the invoice.
• Supplier GSTIN and address: copy-paste from your registration certificate rather than typing it again.
• Recipient GSTIN: double-check every character. A single wrong character means your customer may not get the credit.
• Place of supply: the state where the supply is treated as made. This decides which tax applies (see Step 4).

If you also send quotations, you can make them in the same tool. Keep the item lines identical when you later bill the confirmed work, so the client can match the two easily.

Step 3: Add line items with HSN/SAC codes

Each line should let anyone understand exactly what was sold. A good line item has:

| Field | Example | |---|---| | Description | Website maintenance – October 2026 | | SAC/HSN | 998314 | | Quantity / Unit | 1 / month | | Rate | ₹8,000 | | Discount | ₹500 | | Taxable value | ₹7,500 | | GST rate | 18% |

The example code and rate are for illustration only. Always confirm the correct code and rate for your own goods or services.

Keep descriptions specific. "Services" or "Material" invites questions from your customer's accounts team. "Annual AMC for 3 CCTV cameras, Nov 2026 – Oct 2027" does not.

Apply discounts before tax when the discount is given on the invoice itself, so GST is calculated on the reduced taxable value.

Step 4: Choose CGST + SGST or IGST

This is the most common mistake on hand-made invoices. The rule of thumb is simple:

• Intra-state supply (your location and the place of supply are in the same state): the GST rate is split equally into CGST and SGST (or UTGST in a union territory). For an 18% item, that is 9% CGST + 9% SGST.
• Inter-state supply (different states): the full rate is charged as IGST. For an 18% item, that is 18% IGST.

The total tax is the same either way; only the heads change. Doffl's invoice generator calculates CGST, SGST and IGST for you, so you don't have to split the tax by hand. If you want to check a figure quickly, the GST/VAT Calculator shows the tax amount and the GST-inclusive or exclusive price for any rate.

Worked example (intra-state, 18%):

• Taxable value: ₹7,500
• CGST 9%: ₹675
• SGST 9%: ₹675
• Invoice total: ₹8,850

For an inter-state customer, the same invoice would show IGST 18%: ₹1,350, with the same total of ₹8,850.

Step 5: Write the total in words and add your signature

Many businesses and banks expect the invoice total in words as well as figures. It reduces the chance of someone misreading or altering the amount. For ₹8,850 you would write: Rupees Eight Thousand Eight Hundred Fifty Only.

Getting lakhs and crores right in words is easy to slip on. The Number to Word Converter turns any amount into words in the Indian numbering format, so you can paste it straight into the invoice.

Finally, the invoice should be signed by you or an authorised person. If you send PDF invoices, you can add a company seal image made with the Digital Stamp Creator alongside the signature. Check with your customer whether they also need a digitally signed PDF.

Step 6: Review, download and send

Before you download the PDF, run through this quick checklist:

• [ ] Invoice number is the next one in the series and not used before
• [ ] Your GSTIN and the customer's GSTIN are correct
• [ ] Place of supply matches the customer's state (or the delivery state for goods)
• [ ] CGST + SGST for same state, IGST for a different state
• [ ] Each line has HSN/SAC, quantity, rate and taxable value
• [ ] Totals add up and the amount in words matches the figure
• [ ] Bank details or UPI ID and due date are shown
• [ ] Signature is present

Then download the PDF and email it, or share it on WhatsApp. Name the file clearly, for example INV-2026-27-0045_ClientName.pdf, so both sides can find it later.

Common invoice mistakes to avoid

• Charging CGST + SGST on an inter-state sale. The customer may not be able to claim the credit and will ask for a corrected invoice.
• Duplicate invoice numbers. This often happens when two people make invoices from copied files. Using one tool with a saved history avoids it.
• Missing customer GSTIN on B2B invoices, which can block their input tax credit.
• Rounding errors. Round only the final total, not each tax line separately, unless your accountant tells you otherwise.
• Old tax rates. Rates are revised from time to time. Check the latest official rate list before you bill a new type of item.
• No payment terms. "Due within 15 days" plus your UPI ID gets you paid faster than a bare amount.

Larger businesses may also need to generate e-invoices through the government's Invoice Registration Portal. Whether that applies to you depends on your turnover and the current notification, so check the latest official rules.

Conclusion

A good GST invoice comes down to a few exact details: a clean invoice number series, correct GSTINs, the right place of supply, HSN/SAC on every line, and the correct tax split. Collect your details once, use a tool that calculates the tax heads for you, and run the checklist before sending.

Try the Quotation/Invoice Generator for your next bill, and keep the Number to Word Converter and GST/VAT Calculator open for quick checks.