GST Invoicing and Splits: The Complete Guide for Small Businesses

Last Updated: June 2026 • By Tushar Gupta

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For small business owners, freelancers, and retail merchants, navigating tax compliance is an essential part of daily operations. Ever since the introduction of the Goods and Services Tax (GST) in India, understanding how to structure invoice pricing has become critical. A simple mathematical error on an invoice can lead to filing inconsistencies, cash flow imbalances, or friction with your clients. This guide explains the core principles of GST, inclusive vs. exclusive tax calculations, and how to split CGST, SGST, and IGST correctly.

1. The Fundamentals of Indian GST

The Goods and Services Tax (GST) is a comprehensive, multi-stage, destination-based tax levied on the supply of goods and services. By replacing numerous indirect taxes (like VAT, Service Tax, and Excise Duty), it was designed to create a unified national market.

Depending on where a transaction originates and where it ends, the GST is split into three main components:

• CGST (Central GST): The tax collected by the Central Government on intra-state supplies (transactions within the same state).
• SGST (State GST): The tax collected by the State Government on intra-state supplies. For Union Territories, this is replaced by UTGST (Union Territory GST).
• IGST (Integrated GST): The tax collected by the Central Government on inter-state supplies (transactions between different states or import/export activities).

For local (intra-state) sales, the total GST rate is split equally between the Central and State governments. If the GST rate is 18%, the invoice will show 9% CGST and 9% SGST. For out-of-state (inter-state) sales, the full 18% is applied as IGST.

2. GST Exclusive Calculations (Tax Extra)

An "Exclusive" GST calculation is used when the advertised price of a product or service does not include the tax amount. The tax percentage is added on top of the base price. This structure is common in B2B (business-to-business) contracting and manufacturing.

The Exclusive Formulas

GST Amount = Base Price × (GST Rate / 100)
Total Price = Base Price + GST Amount

Practical Example

If you are charging a client a base fee of ₹20,000 for a professional service subject to 18% GST within the same state:

1. Calculate GST Amount: GST = ₹20,000 × (18 / 100) = ₹3,600
2. Determine Total Price: Total = ₹20,000 + ₹3,600 = ₹23,600
3. Split the GST (Intra-state): CGST (9%) = ₹1,800, SGST (9%) = ₹1,800

Your invoice will list a base value of ₹20,000, CGST of ₹1,800, SGST of ₹1,800, and a final payable amount of ₹23,600.

3. GST Inclusive Calculations (Tax Included)

An "Inclusive" GST calculation is used when the retail price already includes the tax amount. The buyer pays the final price, and the seller must reverse-calculate the tax portion to report it to the authorities. This structure is standard in B2C retail, restaurants, and consumer electronics.

The Inclusive Formulas

Base Price = Total Price / (1 + GST Rate / 100)
GST Amount = Total Price - Base Price

Practical Example

If you run a retail shop and sell a consumer product for a total price of ₹11,800 (which includes an 18% GST rate) to a local customer:

1. Calculate the Base Price: Base = ₹11,800 / (1 + 18 / 100) = ₹11,800 / 1.18 = ₹10,000
2. Calculate the GST Amount: GST = ₹11,800 - ₹10,000 = ₹1,800
3. Split the GST (Intra-state): CGST (9%) = ₹900, SGST (9%) = ₹900

For your accounting books, the revenue is ₹10,000, and the remaining ₹1,800 is a tax liability split equally between CGST and SGST.

4. Overview of Major GST Tax Slabs in India

The GST Council divides goods and services into five major tax brackets:

Slab Rate	Common Categories / Examples
0% (Exempt)	Fresh milk, vegetables, food grains, books, and essential items.
5%	Packaged foodstuffs, tea, coffee, life-saving medicines, and basic transport services.
12%	Processed foods, butter, cheese, business class air travel, and standard apparel.
18% (Standard)	Software services, consulting fees, telecom services, restaurants, and industrial goods.
28% (Luxury/Demerit)	Automobiles, tobacco products, carbonated soft drinks, and high-end consumer electronics.

5. Best Practices for Business Invoicing

To maintain clean books and avoid auditing issues:

• Determine correct HSN/SAC codes: Every product (HSN) and service (SAC) has a specific classification code. Ensure you apply the correct code to determine the accurate tax slab.
• Always verify the buyer's GSTIN: If you are selling to another business (B2B), double-check their GSTIN to ensure they can claim Input Tax Credit (ITC).
• Clear display of CGST & SGST: Make sure your invoicing template splits the CGST and SGST clearly. Lumping them together as one value is not legally compliant in India.