GST — Goods & Services Tax Complete Beginner’s Guide
From the basics of what GST is and how it works, to registration thresholds, types of registration, documents required, and step-by-step online application — everything a business owner needs to know in one place.
What Is GST? — India’s Biggest Tax Reform Since Independence
The Goods and Services Tax (GST) was introduced in India on 1 July 2017 as a comprehensive, multi-stage, destination-based tax. It replaced a web of central and state taxes — including Central Excise Duty, Service Tax, VAT, CST, Entry Tax, Octroi, and over a dozen others — with a single unified indirect tax structure.
The core philosophy is simple: tax should be levied only on value addition at each stage, and the final burden should rest entirely on the end consumer. Every registered business in the supply chain can claim credit for the GST paid on inputs, ensuring there is no cascading “tax on tax” effect.
Before GST, a manufacturer in Delhi selling to a retailer in Mumbai faced: Central Excise Duty + CST + VAT + entry tax + possibly octroi. Each tax was calculated on a base that already included other taxes — creating a cascading tax effect. GST eliminated all of this with a single number on the invoice: the GST rate. India’s indirect tax collection efficiency improved dramatically, and the number of indirect taxpayers has more than doubled since 2017.
CGST, SGST, IGST — The Three Pillars of GST
GST in India is a dual-structure tax — both the Centre and the State simultaneously levy tax on the same transaction. How it splits depends on whether the sale is within the same state (intra-state) or between two states (inter-state).
| Tax Component | Full Form | Applies When? | Who Gets It? |
|---|---|---|---|
| CGST | Central Goods & Services Tax | Intra-state supply (within same state) | Central Government — 50% of GST |
| SGST | State Goods & Services Tax | Intra-state supply (within same state) | State Government — 50% of GST |
| IGST | Integrated Goods & Services Tax | Inter-state supply (across states) or imports | Central Govt, then distributed to consuming state |
| UTGST | Union Territory GST | Supply within a Union Territory (without legislature) | Union Territory — equivalent of SGST |
Intra-state: A Hyderabad trader sells goods at 18% GST to a Hyderabad buyer → Buyer pays 9% CGST + 9% SGST (total 18%).
Inter-state: The same trader sells to a Chennai buyer → Buyer pays 18% IGST (collected by Centre, then distributed to Tamil Nadu).
The seller in both cases charges the same total rate; the split behind the scenes doesn’t affect the buyer’s payment.
Input Tax Credit (ITC) — The Key Benefit of GST
Every GST-registered business that makes taxable outward supplies can claim credit for GST paid on its inputs (purchases, raw materials, services) against its GST liability on outputs. This prevents the cascade effect and ensures tax is paid only on the net value addition at each stage.
Manufacturer buys raw material: pays GST of ₹10,000. Makes a finished product and charges customer GST of ₹18,000. Net GST payable to government = ₹18,000 − ₹10,000 = ₹8,000 only. The ₹10,000 already paid upstream is his ITC — claimable as a credit. Composition scheme dealers and final consumers cannot claim ITC.
Mandatory GST Registration — Are You Required to Register?
GST registration is mandatory when your aggregate turnover in a financial year crosses the prescribed threshold — or when you fall into any of the mandatory registration categories regardless of turnover.
Turnover Thresholds for Mandatory Registration
| Business Type | Normal States | Special Category States* |
|---|---|---|
| Supplier of Goods | ₹40 lakh | ₹20 lakh |
| Supplier of Services | ₹20 lakh | ₹10 lakh |
| Supplier of Both Goods & Services | ₹20 lakh | ₹10 lakh |
*Special Category States: Arunachal Pradesh, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim, Tripura, Uttarakhand, Himachal Pradesh, J&K
Mandatory Registration Regardless of Turnover
- Persons making inter-state taxable supply of goods (service providers exempt up to ₹20L/₹10L)
- E-commerce sellers (Amazon, Flipkart, Meesho, Swiggy) — mandatory regardless of turnover
- Persons liable to pay tax under Reverse Charge Mechanism (RCM)
- E-commerce operators (platforms collecting TCS)
- Foreign persons supplying OIDAR services to India
- Government departments/PSUs deducting TDS under GST
- Claim Input Tax Credit on purchases and reduce tax cost
- Sell to GST-registered businesses (B2B) that require a GSTIN
- Enhance business credibility and compete for tenders
- Export goods/services with zero GST and claim refund
8 Types of GST Registration — Which One Applies to You?
Composition Scheme vs Regular — Quick Comparison
| Feature | Regular Taxpayer | Composition Scheme |
|---|---|---|
| Tax Rate | Standard GST rates (5% / 12% / 18% / 28%) | 1% (traders) / 5% (restaurants) / 6% (services) of turnover |
| Input Tax Credit | Can Claim ITC | Cannot Claim ITC |
| Tax Invoice | Must issue Tax Invoice | Can only issue Bill of Supply (no tax charged) |
| Returns | Monthly / Quarterly GSTR-1, GSTR-3B | Quarterly CMP-08; Annual GSTR-4 |
| Inter-State Supply | Allowed | Not Allowed |
| E-Commerce Sales | Allowed | Not Allowed |
| Turnover Cap | No cap | ₹1.5 crore (goods) / ₹50 lakh (services) |
Documents Required for GST Registration — Complete Checklist
Documents required vary slightly based on the type of entity. Below is the comprehensive list covering all common business structures. All documents must be uploaded in JPEG/PNG/PDF format, generally under 1 MB each, on the GST portal (gst.gov.in).
Common Documents — All Applicants
Additional Documents by Entity Type
| Entity Type | Additional Documents Required |
|---|---|
| Proprietorship | No additional documents — PAN, Aadhaar, address proof, bank account are sufficient |
| Partnership Firm | Partnership Deed (registered) / Partnership Registration Certificate; PAN & Aadhaar of all partners |
| LLP | LLP Agreement; Certificate of Incorporation from MCA; PAN & Aadhaar of all designated partners |
| Private / Public Limited Company | Certificate of Incorporation; MOA & AOA; Board Resolution authorising signatory; PAN & Aadhaar of directors |
| Hindu Undivided Family (HUF) | HUF Deed (if any); PAN of HUF; Aadhaar & photo of Karta |
| Society / Trust / NGO | Registration Certificate under Societies Registration Act / Indian Trusts Act; Trust Deed; PAN of entity; Aadhaar of authorised person |
| Government Department | Authorisation letter; Department PAN; Aadhaar of authorised officer |
As per CBIC Instruction No. 03/2025-GST dated 17 April 2025, GST registration applicants are now subject to physical verification of place of business and biometric authentication of Aadhaar at GST Suvidha Kendras (GSKs). The applicant must visit the designated GSK within 15 days of filing the registration application to complete biometric verification. Failure to do so results in the ARN not being generated and the application being deemed withdrawn. Always check the portal for the nearest GSK in your district before applying.
Step-by-Step GST Registration Process Online
Select “New Registration”, choose “Taxpayer” in the dropdown. Select your state, district, and enter your PAN, mobile, and email. OTP will be sent to both mobile and email.
After OTP verification, a TRN is generated. Use the TRN to complete the full registration form within 15 days. Save the TRN — the application remains incomplete if the form isn’t submitted within this window.
Complete all business details: trade name, principal place of business, additional places (if any), business activity (commodity/service codes using HSN/SAC), authorised signatory, and bank account details. Upload all required documents.
An Aadhaar authentication link is sent to the registered mobile/email. Complete OTP-based authentication online. If biometric authentication is triggered (high-risk states or flagged cases), visit the designated GSK for physical biometric verification.
Submit the application using DSC (companies/LLPs) or e-Signature/EVC (proprietors/partners). On successful submission, an Application Reference Number (ARN) is generated. The application status can be tracked using ARN on the GST portal.
If everything is in order, the GST officer approves the application and issues the GSTIN and GST Registration Certificate. If clarification is needed, you receive a notice on the portal (Form GST REG-03) and must respond within 7 working days.
Download the GST Registration Certificate (Form GST REG-06) from the portal. Display it prominently at your principal place of business. Add your bank account within 30 days of GSTIN allotment to avoid suspension of the registration.
Penalty of 100% of tax due or ₹10,000, whichever is higher, under Section 122 of CGST Act. Additionally, GST collected from customers without registration is treated as a criminal offence. The GST department’s AI-powered analytics now cross-match ITR data, TDS returns, bank transactions, and e-way bills — unregistered businesses above the threshold are increasingly being flagged and issued show-cause notices automatically.
Key GST Returns — What Every Registered Business Must File
| Return Form | Who Files | Frequency | Due Date |
|---|---|---|---|
| GSTR-1 | Regular taxpayers — outward supply details | Monthly (turnover >₹5 Cr) / Quarterly (QRMP) | 11th of next month / 13th of month after quarter |
| GSTR-3B | Regular taxpayers — summary return with tax payment | Monthly / Quarterly (QRMP) | 20th / 22nd / 24th of next month |
| GSTR-4 | Composition scheme taxpayers | Annual | 30 April of following year |
| CMP-08 | Composition scheme — quarterly tax payment | Quarterly | 18th of month after quarter |
| GSTR-9 | Regular taxpayers — annual return | Annual | 31 December of following year |
| GSTR-9C | Taxpayers with turnover >₹5 crore — reconciliation | Annual | 31 December of following year |
2. CGST Act, 2017 — Section 22 (mandatory registration threshold), Section 10 (composition scheme), Section 24 (mandatory registration categories), Section 122 (penalty for non-registration)
3. CBIC Instruction No. 03/2025-GST (17 April 2025) — biometric authentication and physical place of business verification for GST registration
4. GSTN Advisory (20 November 2025) — bank account must be provided within 30 days of GSTIN allotment or before first GSTR-1 filing
5. GST Registration Thresholds (effective from 1 April 2019 — unchanged): ₹40L goods / ₹20L services (normal states); ₹20L / ₹10L (special category states)
6. Composition Scheme limits: ₹1.5 crore (goods, normal states) / ₹75 lakh (special states); ₹50 lakh (service providers); CMP-02 for annual opt-in
7. ISD mandatory registration from 1 April 2025 (Finance Act 2024 amendment to CGST Act)