GST registration for small businesses: when it is mandatory and how to apply

You must register for GST when your aggregate turnover in a financial year crosses ₹40 lakh for goods or ₹20 lakh for services (₹20 lakh and ₹10 lakh in special category states), or immediately, regardless of turnover, if you sell goods to another state, sell through an e-commerce operator, or are liable under reverse charge. Registration is free on gst.gov.in, takes about a week, and once registered you must issue tax invoices and file returns every month or quarter.

The turnover limits, and what "aggregate turnover" means

Section 22 of the CGST Act, 2017 says every supplier must register in the state from where they make taxable supplies once their aggregate turnover in a financial year exceeds the threshold. The thresholds as they stand in FY 2026-27 are below. Confirm the position for your state on the portal because a few states have chosen a different limit.

The ₹40 lakh limit for goods came through Notification 10/2019-Central Tax and applies only if you supply goods and nothing else. If you also provide even a small amount of services (say, installation charges billed separately), the ₹20 lakh limit applies. The ₹10 lakh limit applies in Manipur, Mizoram, Nagaland and Tripura; some other hill and north-eastern states opted to stay at ₹20 lakh for goods. Check the current list before you rely on the higher limit.

"Aggregate turnover" is defined in Section 2(6). It is the total value of all your supplies under one PAN across all of India, and it includes:

• Taxable supplies
• Exempt and nil-rated supplies
• Exports
• Inter-state supplies between your own branches

It excludes GST itself and the value of inward supplies on which you pay tax under reverse charge. This matters because many people count only their taxable sales. A Kochi electronics shop that sells ₹30 lakh of taxable goods and ₹12 lakh of exempt goods has an aggregate turnover of ₹42 lakh and must register, even though its taxable turnover is well under ₹40 lakh.

Who must register regardless of turnover

Section 24 lists categories where registration is compulsory from the first rupee. For a small business, the ones that bite are:

1. Inter-state supply of goods. If you ship goods from Surat to a buyer in Mumbai, you need registration before that first sale. Inter-state supply of services is relaxed: service providers get the benefit of the ₹20 lakh limit even for inter-state supplies (Notification 10/2017-Integrated Tax). Handicraft makers also have a relaxation up to ₹20 lakh for inter-state supply of specified handicraft goods.
2. Selling through an e-commerce operator. If you list on a marketplace that collects TCS, you generally need registration. There are relaxations: intra-state suppliers of goods and services below the threshold can sell through an e-commerce operator without registration if they meet certain conditions (enrolment number, no inter-state supply). The conditions change; confirm the current position before listing without a GSTIN.
3. Reverse charge liability. If you receive goods or services on which you, the recipient, must pay tax (goods transport agency services, advocate fees, import of services, and so on), you must register to pay that tax.
4. Casual taxable person. If you set up a stall at a trade fair in another state, you need a casual registration there, with advance tax deposit.
5. Non-resident taxable persons, input service distributors, TDS and TCS deductors, and agents who supply on behalf of others.

Registration must be applied for within 30 days of becoming liable (Section 25(1)). Casual and non-resident persons must apply at least 5 days before starting business.

Voluntary registration: when it makes sense and when it does not

Section 25(3) lets you register voluntarily below the threshold. Once you do, every provision of the Act applies to you as if you were compulsorily registered. That means monthly or quarterly returns, tax invoices, and tax on every taxable sale from day one.

Voluntary registration helps when:

• Your customers are businesses that want input tax credit. A Pune freelance designer billing agencies will lose clients if they cannot claim ITC on her fees.
• You buy a lot of taxable inputs and want to claim credit on them rather than treating the GST as cost.
• You want to sell on marketplaces or ship to other states.
• You want to bid for tenders or work with large companies whose vendor onboarding requires a GSTIN.

It hurts when:

• Your customers are mostly consumers who cannot claim credit. Adding 18% to a ₹10,000 tuition fee makes you 18% more expensive than an unregistered neighbour.
• Your compliance capacity is thin. Late fees and interest, explained in our guide to GST late fees and penalties, apply to voluntary registrants too.
• Your inputs carry little GST (rent from an unregistered landlord, wages, small local purchases).

A simple test: estimate the GST you would collect from customers who cannot claim it, subtract the ITC you would gain on purchases, and weigh the difference against the compliance cost. If you are close to the threshold anyway, register early so you are not caught unprepared in the month you cross it.

Documents you need

Keep scanned copies ready in JPEG or PDF at the sizes the portal accepts (usually 100 KB for photographs and 1 MB for other documents). The exact list depends on your constitution.

The address proof is where most applications get stuck. If you work from a rented shop, upload the rent agreement and the landlord's electricity bill. If you work from home, a consent letter from the owner (even a family member) plus their electricity bill works. The document should be recent and the address should match what you type in the form character by character.

Step by step on the GST portal

1. Go to gst.gov.in, choose Services, Registration, New Registration. Select "Taxpayer", pick your state and district, enter the legal name exactly as on PAN, PAN, email and mobile. Verify the OTPs. You receive a Temporary Reference Number (TRN).
2. Log in with the TRN and complete Part B of Form GST REG-01. It has tabs for business details, promoters or partners, authorised signatory, principal place of business, additional places, goods and services (enter the top HSN or SAC codes; see our HSN and SAC guide), state-specific information, and Aadhaar authentication.
3. In the business details tab, choose whether you want the composition scheme. If you are a trader, manufacturer or restaurant with turnover under ₹1.5 crore, read our composition scheme explainer before you tick that box.
4. Complete Aadhaar authentication for the promoter and authorised signatory. Applications without Aadhaar authentication go for physical verification of the premises and take longer.
5. Submit with EVC (OTP) or DSC. Companies and LLPs must use a DSC.
6. You get an Application Reference Number (ARN) by email and SMS. Track it under Services, Registration, Track Application Status.
7. If the officer needs clarification, you receive Form GST REG-03. Reply in REG-04 within 7 working days. If you do not respond, the application is rejected in REG-05 and you start again.
8. On approval, you receive the registration certificate in Form GST REG-06 with your 15-digit GSTIN. Download it from the portal; it is not posted.

Rule 9 gives the officer 7 working days to approve or query an Aadhaar-authenticated application, and up to 30 days where physical verification is needed. In late 2025 the GST Council also announced a simplified registration track for low-risk applicants with approval targeted within 3 working days; check the portal for whether you qualify.

Reading your GSTIN

The GSTIN has a fixed structure: two digits for the state code, ten characters for the PAN, one character for the entity number under that PAN in the state, the letter Z, and a check digit. 27AAAPL1234C1Z5 is a Maharashtra registration (27) for PAN AAAPL1234C. Before you record a new customer or vendor, verify their GSTIN and legal name with the GSTIN checker. A wrong GSTIN on a tax invoice means your customer's ITC will not show in their GSTR-2B.

What changes the day you are registered

Invoices. Every taxable sale needs a tax invoice under Section 31 and Rule 46 with your GSTIN, a serial number, date, the customer's GSTIN if registered, HSN or SAC, taxable value, rate, and the CGST and SGST or IGST amounts. The full field list is in our GST invoice guide. The invoice series must be consecutive and unique for the financial year.

Tax on sales. You must charge GST at the correct rate on every taxable supply, including sales to consumers. You can absorb it in your price or add it on top, but the invoice must show it. Use the GST calculator when you need to work backwards from an inclusive price.

Returns. Regular taxpayers file GSTR-1 (sales) by the 11th and GSTR-3B (summary and payment) by the 20th of the next month, or quarterly under QRMP if turnover is up to ₹5 crore. See our GSTR-1 and GSTR-3B filing guide. Even a month with zero sales needs a nil return.

Input tax credit. You can now claim credit for the GST paid on business purchases, subject to the conditions in our ITC guide. You can also claim credit on stock held on the day before registration by filing Form GST ITC-01 within 30 days (Section 18(1)).

Display. Rule 18 requires your GSTIN on the name board at every place of business and the registration certificate displayed at the principal place.

Records. Keep purchase and sales registers, stock records, and copies of invoices for 72 months from the due date of the annual return (Section 36).

A worked example: a Surat textile trader crossing the limit

Ramesh runs a saree wholesale shop in Surat. His sales, all within Gujarat, were ₹31 lakh in FY 2025-26. In FY 2026-27 business picks up:

He crosses ₹40 lakh on some day in September. From that day he is liable and must apply within 30 days. Until his GSTIN is issued he cannot collect tax, but he can claim ITC on stock held on the day before he becomes liable through ITC-01. If he had shipped one consignment to a Mumbai buyer in April, he would have needed registration before that shipment, regardless of the ₹40 lakh limit.

If Ramesh instead sold ₹30 lakh of sarees and also earned ₹2 lakh from stitching services, his threshold would be ₹20 lakh, not ₹40 lakh, and he would have crossed it long ago.

Common mistakes

• Counting only taxable sales. Exempt sales, exports and branch transfers all count towards the threshold.
• Waiting for the invoice to be raised. Liability starts when you cross the limit, not when you notice it. Late registration means tax for the unregistered period is payable from your own pocket, with interest, and you cannot recover it from customers.
• Typing a different address than the proof. "Shop 4, Ring Road" on the form and "Shop No. 4, Ring Rd" on the bill invites a REG-03 query.
• Ignoring the REG-03 notice. Seven working days is short. Check the email and the portal daily after applying.
• Choosing composition without understanding it. Composition dealers cannot make inter-state sales or claim ITC.
• Forgetting nil returns. The late fee runs even when sales are zero.
• Registering in one state and operating from another. You need a separate registration in every state from which you supply.

How VyaparKit helps

Once you have a GSTIN, the GST invoice tool produces compliant tax invoices with FY-wise numbering, HSN or SAC, and automatic CGST, SGST or IGST split based on the place of supply. Use the GSTIN checker to verify every customer and vendor before you save them. The GST due dates calendar shows the filing dates for your scheme, and the GST calculator helps you quote inclusive and exclusive prices correctly. VyaparKit does not file returns for you; it gets your documents and registers in order so filing is quick.

Next steps

• Work out your aggregate turnover for the current and previous financial year, including exempt sales.
• Check whether any Section 24 category applies to you (inter-state goods, marketplace, reverse charge).
• Gather PAN, Aadhaar, photograph, address proof and bank proof, and match the address text exactly.
• Apply on gst.gov.in, note the ARN, and watch for a REG-03 query.
• On approval, set up your invoice series, HSN codes and return calendar before the first taxable sale.