Everything you need to know about creating legally valid, GST-compliant invoices in India — from mandatory fields to tax calculations and common mistakes.
A GST invoice (also called a tax invoice) is a formal commercial document issued by a GST-registered supplier to a buyer when a taxable supply of goods or services takes place. Under the Goods and Services Tax (GST) Act of India, which came into effect on 1 July 2017, every registered taxpayer is legally required to issue a tax invoice for every taxable transaction.
The invoice acts as the primary document that allows the buyer (if they are a registered business) to claim Input Tax Credit (ITC) — meaning they can deduct the GST they paid from the GST they owe to the government. Without a proper tax invoice, the buyer cannot claim ITC, which has significant financial and compliance implications.
A GST invoice is different from a regular invoice in that it must specifically state the applicable GST rates, the breakdown of CGST, SGST, or IGST amounts, and the GSTINs of both the supplier and recipient. A regular invoice (also called a commercial invoice) does not carry these tax-specific details and cannot be used for ITC claims.
Under GST law, there are several types of invoices depending on the situation:
Every person who is registered under GST must issue a tax invoice when making a taxable supply. Registration under GST is mandatory when your annual turnover exceeds the prescribed threshold limits:
| Business Type | Registration Threshold | Special Category States |
|---|---|---|
| Goods supplier (regular states) | ₹40 lakhs per year | ₹20 lakhs per year |
| Service provider | ₹20 lakhs per year | ₹10 lakhs per year |
| E-commerce operators (all) | Mandatory regardless of turnover | Mandatory |
| Inter-state suppliers | Mandatory regardless of turnover | Mandatory |
| Casual taxable persons | Mandatory regardless of turnover | Mandatory |
Even if you are not required to register, you can voluntarily register for GST if you want to claim ITC on your purchases or if your clients require you to have a GSTIN. Voluntary registration gives you the same rights and obligations as a mandatory registrant.
Rule 46 of the CGST Rules 2017 specifies all the information that must appear on a tax invoice. Missing even one mandatory field can make the invoice invalid for ITC purposes and may attract penalties from tax authorities.
India's GST is a dual tax structure — both the Central Government and the State Government have the right to levy tax on the same transaction. The type of GST that applies depends on whether the supply is within a state (intra-state) or between two different states (inter-state).
CGST is levied by the Central Government on intra-state supplies. If you are selling to a customer in the same state as your business, you charge CGST. The CGST rate is always exactly half of the total GST rate. For example, if the GST rate is 18%, CGST is 9%.
SGST is levied by the State Government on intra-state supplies alongside CGST. It is always equal to CGST — half the total GST rate. The SGST collected goes to the state government where the supply takes place. For a supply taxed at 18% GST, SGST is 9%.
IGST is levied by the Central Government on inter-state supplies — when the supplier and the buyer are in different states or union territories. The full GST rate is applied as IGST (no split). So for 18% GST on an inter-state supply, you charge IGST at 18%. The Central Government then apportions IGST between itself and the destination state.
| Tax Type | Levied By | When Applied | Rate Example (18% GST) | Goes To |
|---|---|---|---|---|
| CGST | Central Govt | Same state (intra-state) | 9% | Central Government |
| SGST | State Govt | Same state (intra-state) | 9% | State Government |
| IGST | Central Govt | Different states (inter-state) | 18% | Central Govt (shared with dest. state) |
| UTGST | Union Territory | Supplies within Union Territories | 9% | Union Territory |
For goods, the place of supply is generally the location where the goods are delivered. For services, it is slightly more complex and depends on the nature of the service. For most B2B services, the place of supply is the location of the recipient. For B2C services, it is the location of the supplier. When in doubt, consult a Chartered Accountant to determine the correct place of supply for your specific transaction type.
GST in India is structured into four main rate slabs. The GST Council, which includes the Finance Ministers of all states and the Union Finance Minister, periodically revises which goods and services fall under each slab. Below is a comprehensive breakdown:
| Rate | Category | Common Examples |
|---|---|---|
| 0% (Exempt) | Essential goods and services | Fresh vegetables, milk, eggs, bread, books, educational services, healthcare, agriculture |
| 5% | Basic necessities | Packed food items, restaurant food (non-AC), economy class air travel, life-saving drugs, fertilizers, handloom fabrics |
| 12% | Standard goods & services | Processed food, mobile phones, computers, furniture, business class air travel, hotels (₹1,000–₹7,500/night), construction services |
| 18% | Most goods & services | IT services, software, financial services, telecom, most manufactured goods, restaurants (AC), hotels (above ₹7,500/night), professional services |
| 28% | Luxury & sin goods | Luxury cars, motorcycles above 350cc, tobacco products, aerated beverages, cement, washing machines, air conditioners, gambling, casinos |
For services, some commonly applicable GST rates are as follows (subject to change):
HSN (Harmonised System of Nomenclature) codes are internationally standardised 8-digit codes used to classify goods. SAC (Service Accounting Codes) are 6-digit codes used to classify services under GST. These codes must appear on your tax invoice depending on your annual turnover.
| Annual Turnover | HSN Digits Required | Applicability |
|---|---|---|
| Up to ₹1.5 crore | Not mandatory | Optional for goods; not required for services |
| ₹1.5 crore to ₹5 crore | 2-digit HSN | Mandatory for goods; SAC optional for services |
| Above ₹5 crore | 4-digit HSN | Mandatory for all; 6-digit SAC for services |
| Exports and e-invoicing | 8-digit HSN | 8-digit mandatory for all exports and e-invoices |
You can look up HSN and SAC codes on the official GST portal at gst.gov.in under the "GST Rates" section. Some common SAC codes for service businesses:
Using the wrong HSN or SAC code is one of the most common errors in GST invoicing. An incorrect code means your buyer may receive an ITC claim that gets flagged during GST return matching, leading to notices and demands.
Section 31 of the CGST Act 2017 prescribes specific time limits within which a tax invoice must be issued. Issuing an invoice late is a compliance violation and can attract penalties.
| Type of Supply | Time Limit to Issue Invoice |
|---|---|
| Supply of goods (excluding continuous supply) | At the time of removal/delivery of goods |
| Supply of services (excluding continuous supply) | Within 30 days from date of supply of service |
| Continuous supply of goods | On or before the date of issuance of statement or when payment is received |
| Continuous supply of services | On or before the due date of payment as per the contract |
| Supply by banking/financial institutions and insurance companies | Within 45 days from date of supply of service |
| Exports | Before or at the time of removal of goods |
GST rules require that invoice numbers follow a specific structure. According to Rule 46 of the CGST Rules 2017, the invoice number must be:
A recommended format is: INV/2025-26/001 or INV-25-001. The series must restart at the beginning of each financial year. You cannot use the same invoice number twice within a financial year.
These are the most frequently cited reasons for ITC disallowances, GST notices, and audit findings in India. Avoiding these mistakes will keep your business compliant and protect your clients' ITC claims.
Using an incorrect, cancelled, or suspended GSTIN (your own or your client's) invalidates the invoice for ITC purposes. Always verify GSTINs on the GST portal before issuing and never rely on memory alone.
Applying the wrong rate (e.g., 18% when the correct rate is 12%) creates a mismatch in GSTR-2A for your buyer. Any shortage must be paid by the buyer as a demand plus interest.
If the supply is inter-state but you charge CGST+SGST, the entire tax calculation is invalid. The correct tax type is critical for ITC matching in GSTR-2B.
Above the applicable turnover threshold, a missing or incorrect HSN/SAC code can lead to notices. Codes must match the actual nature of the goods or services supplied.
Duplicate invoice numbers create matching problems in GST returns. Each invoice must have a unique serial number within its series for the financial year.
If you issue an invoice but don't report it in GSTR-1 by the due date, your client's GSTR-2B won't show the ITC, and they may face demands. File GSTR-1 on time for every invoice issued.
Late invoices for services (beyond 30 days) are non-compliant. While the buyer may still accept them, the supplier is technically in violation and may face penalties.
The place of supply determines whether CGST+SGST or IGST applies. Leaving it out is a compliance gap. For inter-state supplies especially, it must be clearly stated on the invoice.
If the supply is subject to reverse charge (where the buyer pays the tax), this must be explicitly stated on the invoice. Omitting this declaration creates compliance issues for the buyer.
All tax invoices must be retained for 72 months (6 years) from the due date of filing the annual return. Losing records can result in additional tax demands during an audit if you cannot prove your transactions.
Creating a GST invoice doesn't require expensive accounting software or a CA's involvement for every invoice. For freelancers, consultants, and small businesses, an online invoice generator like GenerateMyBill is the fastest and simplest solution.
Open GenerateMyBill on your mobile or desktop browser. No registration, no login, and no software installation required.
Fill in your business name, address, GSTIN, phone, and email. Upload your logo for branded invoices. Your details are saved automatically for future invoices.
Choose from Classic Blue, Minimal, GST Tax Invoice, or Freelancer templates. Each has a distinct professional design with a different print layout.
Add your client's name, address, and GSTIN. Enter the invoice number, date, due date, and PO number if applicable.
Add your services or products with quantity and rate. Select CGST+SGST or IGST, choose the applicable GST rate (5%, 12%, 18%, or 28%), and apply a discount if needed. All totals calculate in real time.
Click Preview Invoice to see the final result. Download as PDF for your records or use the WhatsApp button to instantly send the invoice to your client.
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