GST Calculator 2026

Goods and Services Tax (GST) is India's unified indirect tax that replaced over a dozen central and state levies — including excise duty, service tax, VAT, CST, and octroi — on 1st July 2017. GST is a destination-based consumption tax, meaning the tax revenue goes to the state where the goods or services are consumed, not where they are produced. This fundamental shift eliminated the cascading tax-on-tax problem and created a single national market.

Exclusive GST calculation. When the listed price does not include GST (common in B2B transactions), the formula is straightforward: GST Amount = Base Price × GST Rate / 100. For example, a laptop priced at ₹50,000 with 18% GST: GST = ₹50,000 × 18/100 = ₹9,000, making the total payable ₹59,000. In an intra-state transaction (buyer and seller in the same state), this ₹9,000 is split equally as ₹4,500 CGST and ₹4,500 SGST.

Inclusive GST calculation. When the MRP or listed price already includes GST (common in B2C retail), you need to extract the base price: Base Price = Total Price × 100 / (100 + GST Rate). For a product priced at ₹1,180 inclusive of 18% GST: Base = ₹1,180 × 100 / 118 = ₹1,000. GST component = ₹180. This reverse calculation is essential for businesses claiming input tax credit — the credit is on the GST component, not the total price.

GST rate slabs in India. GST operates under a multi-rate structure: 0% for essential items (fresh food, healthcare, education); 3% for gold and precious metals; 5% for basic necessities and household items; 12% for processed food and electronics; 18% for most services, software, and manufacturing; and 28% for luxury goods, automobiles, and aerated drinks. Some items in the 28% slab also attract an additional compensation cess (e.g., SUVs, tobacco, pan masala). Use our GST calculator above to compute the exact breakdown for any rate and amount.

A practical tip for small businesses: always verify the correct HSN/SAC code on the CBIC portal before issuing invoices. The GST rate is determined by the HSN (Harmonized System of Nomenclature) code for goods and SAC (Services Accounting Code) for services — applying the wrong code can lead to incorrect tax collection and penalties during audit.

Understanding the three components of GST is fundamental to correct invoicing, return filing, and input tax credit utilisation. The distinction is based entirely on the location of the supplier and recipient — whether the transaction crosses state borders determines which component applies.

CGST (Central GST) + SGST (State GST) — Intra-state transactions. When both buyer and seller are in the same state, GST is split equally between CGST and SGST. For example, a ₹10,000 service with 18% GST in an intra-state transaction: CGST = 9% = ₹900 (goes to the Central Government) and SGST = 9% = ₹900 (goes to the State Government). Both must be shown separately on the invoice. For Union Territories (like Chandigarh, Ladakh, Andaman & Nicobar), UT-GST replaces SGST — the rate and rules are identical, only the name and the receiving authority differ.

IGST (Integrated GST) — Inter-state transactions. When the supplier and recipient are in different states, IGST is charged at the full GST rate. For the same ₹10,000 service at 18%, inter-state IGST = ₹1,800 — collected as a single component and initially deposited with the Central Government, which then settles the state's share. IGST also applies to all imports into India and to supplies to/from Special Economic Zones (SEZs), even within the same state.

Input Tax Credit (ITC) cross-utilisation. The set-off rules are specific: IGST credit can be used to offset IGST, then CGST, then SGST liability — in that order. CGST credit can offset CGST and then IGST (but never SGST). SGST credit can offset SGST and then IGST (but never CGST). This means businesses dealing in both intra-state and inter-state transactions must carefully plan their ITC utilisation to avoid leaving credit stranded in one component while paying cash in another. Our income tax calculator can help assess the overall tax burden including GST impact on your business.

Place of supply rules. Determining whether a transaction is intra-state or inter-state depends on the place of supply under the IGST Act. For goods, the place of supply is generally where the movement of goods terminates (the delivery address). For services, the rules are more nuanced — the recipient's location determines the place of supply in most cases, but exceptions exist for immovable property (location of property), restaurants (location of restaurant), and events (location of event). Incorrect determination of place of supply is one of the most common GST compliance errors and can lead to wrong tax type being charged (CGST+SGST instead of IGST or vice versa).

Input Tax Credit is the backbone of the GST system and its greatest advantage for businesses. ITC allows you to reduce your output GST liability by the amount of GST you have already paid on business purchases (inputs, input services, and capital goods). Without ITC, GST would cascade — you would pay tax on tax at every stage of the supply chain, just like the old VAT/excise regime.

Eligibility conditions for claiming ITC. Four conditions must be simultaneously satisfied: (1) You must possess a valid tax invoice or debit note from the supplier. (2) You must have received the goods or services. (3) The supplier must have filed their GSTR-1 and the invoice must reflect in your GSTR-2B. (4) You must have actually paid the tax to the supplier within 180 days of the invoice date — if payment is not made within 180 days, the ITC must be reversed with interest. This 180-day rule catches many businesses off guard, especially those with long payment cycles.

Blocked credits under Section 17(5). Certain purchases are permanently blocked from ITC regardless of their business use: motor vehicles (except for specific business purposes like transport, training, or demo), food and beverages, outdoor catering, beautification/cosmetic surgery, health and fitness services, travel benefits for employees (LTC, holiday packages), membership of clubs and health facilities, works contract services for construction of immovable property (except for further supply), and goods or services used for personal consumption. Understanding blocked credits is essential — claiming ITC on blocked items will be reversed during audit with interest and potential penalty.

ITC reversal rules. Beyond blocked credits, ITC must be reversed proportionately when goods are used partly for business and partly for personal purposes, or partly for taxable and partly for exempt supplies. Rule 42 governs reversal for inputs and input services, while Rule 43 applies to capital goods. The annual reconciliation in GSTR-9 (annual return) is where any remaining ITC mismatches are settled. Businesses must also reverse ITC if the supplier defaults on tax payment — this is tracked through the GSTR-2B matching mechanism on the GST portal.

Maximising ITC as a small business. Ensure all your vendors are GST-registered and file returns on time — ITC is only available if the supplier's invoice appears in your GSTR-2B. Maintain proper documentation for every purchase. Time your large capital goods purchases strategically — ITC on capital goods is available immediately in full (no need to spread over the asset's life). For businesses near the ₹40 lakh threshold, the decision between regular registration and the Composition Scheme hinges heavily on ITC — Composition dealers cannot claim any ITC, making it suitable only for businesses with minimal input costs.

GST registration is mandatory for certain businesses and optional (but often beneficial) for others. The registration process is entirely online through the GST portal and must be completed within 30 days of becoming liable. Operating without registration when required attracts heavy penalties — 100% of the tax due or ₹10,000, whichever is higher.

Mandatory registration thresholds. For goods suppliers, registration is required when annual aggregate turnover exceeds ₹40 lakh (₹20 lakh for special category states like Manipur, Mizoram, Nagaland, Tripura, Meghalaya, and Uttarakhand). For service providers, the threshold is ₹20 lakh (₹10 lakh for special category states). Regardless of turnover, registration is mandatory for: inter-state suppliers, e-commerce operators, persons required to deduct TDS/TCS, casual taxable persons, non-resident taxable persons, and agents of registered suppliers.

Composition Scheme — simplified compliance. Small businesses with turnover up to ₹1.5 crore (₹75 lakh for special states) can opt for the Composition Scheme, paying GST at a flat rate — 1% for manufacturers, 5% for restaurants, and 1% for other suppliers. The trade-off: Composition dealers cannot claim ITC, cannot make inter-state supplies, cannot supply through e-commerce platforms, and must file only quarterly returns (CMP-08) instead of monthly. This is ideal for businesses with low input costs and purely local operations — like a neighbourhood bakery or a local retail shop.

Return filing obligations. Regular taxpayers must file: GSTR-1 (outward supplies) by the 11th of the following month; GSTR-3B (summary return with tax payment) by the 20th; and GSTR-9 (annual return) by 31st December. Late filing attracts a penalty of ₹50/day (₹20/day for nil returns) per return, capped at ₹10,000 per return per period. The government has introduced the QRMP (Quarterly Return Monthly Payment) scheme for businesses with turnover up to ₹5 crore — allowing quarterly filing of GSTR-1 and GSTR-3B while paying tax monthly through a challan.

GST audit and reconciliation. While mandatory GST audit by a CA has been abolished for most businesses (from FY 2020-21), the self-certification requirement in GSTR-9C (reconciliation statement) remains for businesses with turnover exceeding ₹5 crore. Even below this threshold, maintaining proper books and reconciling purchase data with GSTR-2B is critical — the department can initiate audit or investigation for any registered person. Our TDS calculator can help you understand TDS obligations that interact with your GST compliance.

The GST landscape for digital-first businesses, freelancers, and e-commerce sellers has distinct rules that differ significantly from traditional brick-and-mortar operations. If you sell online — whether products on Amazon/Flipkart or services as a freelancer — understanding these provisions is essential to avoid compliance gaps and unexpected tax demands.

E-commerce operators and TCS (Tax Collected at Source). Platforms like Amazon, Flipkart, Swiggy, and Zomato are classified as e-commerce operators and must collect TCS at 1% (0.5% CGST + 0.5% SGST for intra-state, or 1% IGST for inter-state) on the net value of taxable supplies made through them. This TCS is deposited with the government and reflected in the seller's electronic cash ledger — it can be claimed as credit when filing GSTR-3B. Sellers supplying through e-commerce platforms must be GST-registered regardless of turnover — the ₹40 lakh threshold exemption does not apply to e-commerce sellers. This catches many small sellers off guard.

Freelancers and service providers. Freelancers providing services (consulting, software development, design, content writing) are liable for GST at 18% once turnover crosses ₹20 lakh (₹10 lakh for special category states). If your clients are outside India and you receive payment in foreign currency, your services may qualify as export of services — zero-rated under GST. This means you charge 0% GST but can still claim ITC on your business expenses, effectively getting a refund. File a Letter of Undertaking (LUT) on the GST portal to supply without payment of IGST. Use our income tax calculator alongside to plan your combined GST and income tax obligations.

Reverse Charge Mechanism (RCM). In certain cases, the recipient of goods or services must pay GST instead of the supplier. This applies to: services from unregistered persons (when specific notifications apply), legal services from advocates, services from goods transport agencies (GTA), import of services, and sponsorship services. Under RCM, you pay GST as if you were the supplier, but you can immediately claim ITC on the same amount — the net cash impact is often nil, but the compliance burden of self-invoicing and reporting is real. Freelancers and small businesses must track RCM liability carefully in their GSTR-3B.

Practical compliance tips for small businesses. (1) Use GST-compliant accounting software from day one — manual tracking becomes unmanageable even at modest volumes. (2) Reconcile your GSTR-2B with purchase records monthly, not at year-end. (3) If you sell on multiple e-commerce platforms, consolidate TCS data from each platform's dashboard before filing. (4) Maintain a separate bank account for GST collections — treat collected GST as the government's money, not working capital. (5) For export-oriented businesses, apply for LUT renewal before 31st March every year to ensure uninterrupted zero-rated supply. Visit the GST portal regularly for circulars and notifications that may affect your business.