After GST registration: invoicing with your GSTIN

When registration applies

Registration under the Goods and Services Tax is compulsory once aggregate turnover crosses the state threshold, which is generally ₹40 lakh for suppliers of goods and ₹20 lakh for suppliers of services, with lower limits in some special-category states. Certain categories, such as e-commerce operators and non-resident taxable persons, must register regardless of turnover. Check the current limit for your state and activity with your accountant.

On approval you receive a 15-character GSTIN, whose first two digits are the state code and the next ten the PAN of the business. That structure matters for invoicing, because the state code in the GSTIN is compared with the place of supply to decide which tax applies.

The application is made on the GST portal with the PAN of the business, Aadhaar authentication of the promoter, proof of the business address, bank account details and a photograph. The portal issues an Application Reference Number, and the officer normally responds within a few working days, either approving the registration or asking for clarification. Do not issue GST invoices until the GSTIN is allotted; in the interval, keep a record of sales so the first return can account for them.

What a tax invoice must contain

The CGST Rules list the mandatory fields: supplier's name, address and GSTIN; a consecutive invoice number unique for the financial year, not exceeding 16 characters; the date; the recipient's name, address and GSTIN if registered; HSN code for goods or SAC for services; description, quantity and unit; taxable value; the rate and amount of each tax; place of supply; and a signature or digital signature.

The number sequence is the most common failure. If you start the year with INV/26-27/0001, every invoice thereafter continues the series without gaps, and a cancelled invoice is cancelled, not deleted. A hand-typed spreadsheet series will produce a duplicate eventually; a system that assigns the next number removes the risk.

Keep the HSN or SAC code in the product or service list instead of retyping it on each invoice. A consistent code per item also makes your accountant's work on the monthly return shorter.

CGST, SGST and IGST on one example

Take a Pune consultancy billing a Mumbai client ₹1,00,000 for services at the 18 % standard slab. Both parties are in Maharashtra, so the supply is intra-state and the invoice shows CGST 9 % (₹9,000) and SGST 9 % (₹9,000), a total of ₹1,18,000. If the client were in Bengaluru, the supply would be inter-state and the invoice would show IGST 18 % (₹18,000) with the same total.

Other rates exist for specific goods and services, and the rate schedule has changed over time, so confirm the rate for your HSN or SAC code rather than assuming 18 %. The invoice template should accept the rate per line, because a single document can combine items with different rates.

Timing, corrections and exceptions

A tax invoice for services should be issued within 30 days of the supply, and for goods at or before removal or delivery. If a figure is wrong, you issue a credit note or a debit note linked to the original invoice, not a second invoice with the same number. Businesses under the composition scheme issue a bill of supply and cannot charge GST, and exempt supplies also use that document.

Above a notified turnover limit, which has been lowered in stages, a business must also report B2B invoices on the government's Invoice Registration Portal and obtain an IRN. 4invoices does not generate an IRN or talk to that portal, so businesses in that bracket continue to use their GST software for the registration step.

Many small suppliers also forget the reverse charge. For certain notified supplies, the recipient rather than the supplier pays GST, and the invoice or self-invoice must say so. If your business buys services from an unregistered supplier in a notified category, ask your accountant whether this applies, and keep the supporting bill in the same archive as your sales invoices.

Keeping the records straight

GST law expects you to retain records for several years after the annual return due date, and your accountant reconciles your sales with what customers see in their own returns. Missing or inconsistent invoices turn into notices.

A workable routine: set the company details and GSTIN once in 4invoices, issue every invoice from the system, keep the customer's GSTIN in their 4softcrm record, and give the accountant access to the archive before each filing cycle. The returns themselves, GSTR-1 and GSTR-3B, are prepared and filed outside 4b2b.

If a customer asks you to reissue an invoice with a corrected GSTIN, do not overwrite the old file: issue a credit note against the original and a new invoice with the right details, so that the archive shows both steps.

Input tax credit and why invoice quality travels

A registered business can claim input tax credit on GST it pays to suppliers, but only against valid tax invoices that appear in its own auto-generated statement, GSTR-2B, built from what suppliers have reported. If your invoice is wrong or your supplier does not file, your customer's credit is at risk, and a customer who loses credit because of your error will ask you to correct it.

For you the same logic applies on purchases. A credit is claimed only if the bill carries your correct GSTIN, and a supplier unpaid for 180 days can force you to reverse credit already taken. Keep purchase bills and payment evidence together, and reconcile them monthly rather than at year end.

The lesson for invoicing is practical: enter the customer's GSTIN exactly as they gave it, check the state code against the place of supply, and ask them to confirm details before the first invoice instead of after the first filing deadline.

Not if you are below the threshold and not otherwise required to register; you can then issue an ordinary commercial invoice or a bill of supply without charging GST. Once registered, you must issue a GST tax invoice with your GSTIN, a sequential number and the tax breakup. Check the limit for your state and activity with your accountant.

The CGST Rules require a consecutive serial number of not more than 16 characters, using letters, numerals, hyphens or slashes, unique for the financial year. Plan a short prefix, for example INV/26-27/0001, so the whole year's series fits within the limit and never repeats a number. A series that restarts every financial year, with the year in the prefix, never collides with the previous one.

Compare the place of supply with the supplier's state. If both are in the same state, charge CGST and SGST in equal parts. If they are in different states, charge IGST. A registered customer's GSTIN begins with the state code, which helps you decide, but the place-of-supply rules for services have exceptions, so ask your accountant.

No. 4b2b is not connected to the GST Network or the Invoice Registration Portal. 4invoices issues invoices, stores PDFs and payment links; GSTR-1, GSTR-3B and any IRN generation are carried out by your GST software or accountant, and they remain your legal responsibility as the registered taxpayer. Registration, return filing and refunds all take place on the government portals, not inside 4b2b.

Invoices your accountant can work with

Confirm slabs and filings with your accountant; 4b2b keeps the documents tidy.