GST — Goods and Services Tax — replaced a dozen old taxes in 2017 and became the single biggest compliance task for Indian businesses. If you run a small shop, a freelance service, or an online store, you need to know whether you must register, which returns to file, and how to avoid the costly penalties that trip up thousands of small business owners every year. This guide walks you through everything in plain language.
Who Needs to Register for GST?
Registration is mandatory if your annual turnover crosses the following thresholds:
- Service providers: ₹20 lakh per year (₹10 lakh in special category states like Manipur, Nagaland, Uttarakhand, etc.)
- Goods sellers: ₹40 lakh per year (₹20 lakh in special category states)
- E-commerce sellers (any platform): Mandatory registration regardless of turnover
- Interstate suppliers: Mandatory regardless of turnover
When you do NOT need to register for GST: If your annual turnover is below the threshold and you sell only within your state and not on e-commerce platforms, you are exempt. Even so, you can voluntarily register to claim Input Tax Credit (ITC), which often makes it worthwhile for B2B businesses.
Types of GST: CGST, SGST, IGST
India has three types of GST that apply depending on where buyer and seller are located:
- CGST (Central GST): Collected by the central government on intra-state sales. If you sell from Mumbai to a customer in Pune, CGST applies.
- SGST (State GST): Collected by the state government on the same intra-state transaction — alongside CGST. So a 18% GST rate intra-state = 9% CGST + 9% SGST.
- IGST (Integrated GST): Applies on inter-state sales. A Delhi seller shipping to Bengaluru customer pays IGST (e.g., 18% IGST instead of split CGST/SGST). IGST is also applied on imports.
GST Registration — Step-by-Step Process
Registration is done online on the GST portal (gst.gov.in). Here is the process:
- Go to gst.gov.in → Services → Registration → New Registration
- Select taxpayer type (Regular, Composition, etc.), state, and district
- Enter your PAN number — this is linked to your GST number (GSTIN)
- Enter your mobile number and email for OTP verification
- You receive a Temporary Reference Number (TRN). Use it to complete Part B of the application
- Upload documents: PAN card, Aadhaar, bank account statement or cancelled cheque, business address proof (electricity bill, rent agreement), and a passport-size photo
- Submit the application. You'll get an Application Reference Number (ARN)
- GST officer may approve within 7 working days or raise queries. After approval, your 15-digit GSTIN is issued
Key GST Return Forms You Must Know
Once registered, you must file returns regularly. Here are the most common ones:
GSTR-1 — Outward Supplies
GSTR-1 reports all sales you made. If your turnover is up to ₹5 crore, you can file quarterly (QRMP scheme). Otherwise it is monthly. Due date: 11th of the following month (monthly) or the month after the quarter ends.
GSTR-3B — Monthly Summary Return
This is a self-declared summary of outward supplies, ITC claimed, and tax paid. It is filed monthly and must be submitted even if there are no transactions (NIL return). Due date: 20th of the following month for large taxpayers, 22nd/24th for others under QRMP.
GSTR-9 — Annual Return
Filed once a year, this consolidates all monthly/quarterly returns. Mandatory for taxpayers with turnover above ₹2 crore. Due date: 31st December of the following financial year.
How to File GSTR-1 Online — Step by Step
- Log in to gst.gov.in with your GSTIN and password
- Go to Services → Returns → Returns Dashboard
- Select the Financial Year and Return Period, then click Search
- Click on GSTR-1 → Prepare Online
- Add invoices under the relevant sections: B2B sales (with buyer GSTIN), B2C large (interstate sales above ₹2.5 lakh), B2C small (others), export invoices, credit/debit notes
- Review the summary, preview the return, and submit
- File using DSC (Digital Signature Certificate) or EVC (Electronic Verification Code) sent to your registered mobile/email
Input Tax Credit (ITC) — What It Is and How to Claim It
ITC is the most powerful feature of GST. When you pay GST on purchases (inputs), that amount can be deducted from the GST you owe on sales. For example, if you collected ₹18,000 GST from customers but paid ₹12,000 GST to your suppliers, you only pay ₹6,000 net to the government.
To claim ITC:
- You must have a valid tax invoice from the supplier
- The supplier must have filed their GSTR-1 (ITC auto-populates in your GSTR-2B)
- Goods/services must be used for business purposes
- You must file your return on time
ITC cannot be claimed on personal expenses, food and beverages, travel (unless specific), or composition scheme taxpayers.
GST Composition Scheme — Is It Right for Your Small Business?
The Composition Scheme is designed for small businesses with turnover up to ₹1.5 crore (₹75 lakh for most special category states). Under this scheme:
- Pay a fixed lower tax rate: 1% for traders/manufacturers, 5% for restaurants, 6% for service providers
- File only one quarterly return (CMP-08) and one annual return (GSTR-4)
- No need to maintain detailed invoice-level records
Limitations: You cannot collect GST from customers or claim ITC. You cannot make inter-state sales. Not suitable for B2B businesses where buyers need ITC.
Penalties for Late Filing
- Late fee: ₹50/day (₹25 CGST + ₹25 SGST) for regular returns. Reduced to ₹20/day for NIL returns.
- Interest: 18% per annum on unpaid tax amount for each day of delay
- Maximum late fee: Capped at ₹5,000 per return for most taxpayers
Common GST Mistakes and How to Avoid Them
- Wrong GSTIN on invoices: Always double-check buyer and seller GSTINs before issuing invoices
- Mismatch between GSTR-1 and GSTR-3B: Your sales reported in both returns must match or it triggers notices
- Claiming ITC without supplier filing: Check GSTR-2B before claiming — if supplier has not filed, you cannot claim ITC
- Missing the nil return: Even if you had zero sales, file a NIL return to avoid late fees
- Wrong HSN/SAC codes: Each product or service has a mandatory code that must be correctly mentioned on invoices
Free Tools for GST Filing
- GST Portal (gst.gov.in): Official free filing — suitable for basic needs
- ClearTax Free Plan: Easier interface for filing returns, good for beginners
- Zoho Books Free Tier: Handles invoicing and GST returns for businesses with up to 1,000 invoices/year
- TallyPrime (trial version): Widely used desktop software for GST accounting
Important: This guide covers general GST principles for 2026. Tax laws can change. For complex situations — multiple business verticals, export refunds, GST audits, or litigation — always consult a qualified Chartered Accountant (CA).