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What Is Invoice Number and Why It Matters in GST Billing

Vikash

• 5 min read
Invoice Number

When creating a bill under GST, one of the most important elements is the invoice number. If you're a small or micro-business owner in India or the Middle East, you might often wonder what invoice number is and why it is so important in GST billing.

This article will help you understand everything about invoice no., including its purpose, format, examples, where to find it, and how tools like GimBooks make managing it easy and GST-compliant.

What Is the Invoice Number?

An invoice number is a unique code or reference number that is assigned to every invoice or bill a business creates. It helps in tracking sales, maintaining records, and complying with GST rules.

Every time you create a new invoice, you must give it a new invoice number. This number should be unique and follow a sequence.

Why Is Invoice Number Important in GST Billing?

Invoice numbers are not just random numbers. In GST billing, they play a key role in:

  • Identifying and tracking each bill.
  • Maintaining clear and clean business records.
  • Avoiding duplicate entries.
  • Helping in return filings and audits.
  • Ensuring GST compliance.

If you don’t use proper invoice numbers or if they’re not in the right format, your GST return might get rejected or flagged.

What Is Invoice No. in Simple Terms?

You can think of invoice no like a roll number in school. Each student has a different roll number, just like every bill has its invoice number. It helps identify that specific invoice quickly and clearly.

Where Is the Invoice Number on a Receipt?

Usually, the invoice number in the bill is placed at the top of the invoice, often near the date. It may be labeled as:

  • Invoice No.
  • Invoice #
  • Bill No.

If you're using an invoicing tool like GimBooks, you’ll find it auto-generated and placed right at the top of every invoice you create.

What Should an Invoice Number Look Like?

Let’s look at a few invoice number examples to understand how they are formed:

➤ Invoice Number Sample 1:

INV001

➤ Invoice Number Sample 2:

2025/06/001

➤ Invoice Number Sample 3:

GB-MAY-23-001

Each business can create its style, but it must follow a proper and unique invoice no. Format.

Invoice Number Format for GST

Under GST law, there are a few rules for invoice numbering:

  • It should be serially numbered.
  • It can have alphabets and/or numerals.
  • It must be unique for a financial year.
  • The length should not exceed 16 characters.

Here is a standard invoice number format for GST:

INV/2025-26/001

Let’s break it down:

  • INV stands for invoice.
  • 2025-26: financial year.
  • 001: serial number.

Using this type of format makes GST compliance easy and keeps all your invoices well-organized.

How to Get an Invoice Number for Your Business?

You can get an invoice number by:

  1. Manually writing it in your books or registers.
  2. Using Excel or Word to generate numbers in sequence.
  3. Using a digital tool like GimBooks, which auto-generates GST-compliant invoice numbers for you.

Out of all the methods, using software like GimBooks is the most efficient and secure way.

How to Find Invoice Number in Case of Confusion?

Sometimes, business owners misplace or forget their last invoice number. Here's how you can find it:

  • Check your previous invoices (manual or digital copies).
  • Look into your GST return filing records.
  • Use software like GimBooks, where you can search all past invoices with ease.

GimBooks also prevent duplication by warning you if you try to use an already existing number.

What Happens If You Miss Invoice Numbering?

Mistakes in invoice numbers can lead to the following:

  • Mismatch in GST filings.
  • Penalties from tax departments.
  • Audit issues.
  • Confusion in accounting.

Let’s say you send two invoices with the same number. It can make your books look messy and lead to legal trouble during tax filing.

That’s why businesses trust GimBooks; it auto-checks for errors and helps you stay GST-ready.

Tips to Follow for Invoice Numbering

To stay organized and avoid any issues, follow these best practices:

  • Keep the format consistent for the whole year.
  • Use both alphabets and numbers if needed.
  • Don’t skip numbers.
  • Avoid starting fresh in the middle of a financial year.
  • Use a tool like GimBooks to automate the numbering.

How GimBooks Helps with Invoice Numbers

GimBooks is specially made for small and micro-sized businesses. It was launched in 2017 to help simplify invoicing when GST was introduced in India.

Here’s how it helps with invoice numbers:

  • Auto-generates GST-compliant invoice numbers.
  • Suggests smart formats for easy tracking.
  • Avoids duplicate invoice numbers.
  • Stores all previous invoices in one place.
  • Works on mobile to create invoices on the go!

If you're wondering how to find invoice numbers or keep track of your bills, GimBooks is the tool you need.

A Sample Invoice Using GimBooks

Let’s take a look at how a GimBooks invoice number sample might appear:

Invoice No.: GB-INV-2025-001  

Date: June 6, 2025  

Customer Name: Raj Traders  

Amount: ₹5,000  

GSTIN: 27ABCDE1234F1Z5  

This kind of structure is easy to read, professional, and GST-friendly. With GimBooks, you don’t have to worry about formatting it’s done for you.

Benefits of Using Proper Invoice Numbers

Here are some benefits you can enjoy:

  • Improved accounting.
  • Quick GST filing.
  • Clear business insights.
  • Better customer trust.
  • Legal compliance.

Having correct invoice numbers also makes your business look more professional, especially if you deal with other registered companies.

Common Mistakes to Avoid in Invoice Numbering

Even though it's a simple process, many small businesses make these mistakes:

  • Using the same invoice number again.
  • Skipping numbers (like INV001, INV003).
  • Changing formats mid-year.
  • Not backing up past invoices.

All these problems can be avoided if you use a digital tool like GimBooks.

Summing Up

Understanding what is invoice number is is key to running a compliant and organized business. Whether you are creating bills for products or services, having a proper invoice number format helps in easy tracking and smooth GST return filing.

For small and micro-sized businesses, managing invoices can be tough. That’s where GimBooks becomes your best companion. It removes the guesswork, helps you stay GST-compliant, and simplifies your day-to-day billing tasks all from your phone.

Don’t wait for GST notices or confusion during tax filing. Start using GimBooks today and make invoice numbering a stress-free task.

Explore E-invoicing at GimBooks.

To learn more about Invoicing and Accounting, explore GimBook’s informative blog section! 

Invoice smart, invoice right with GimBooks.

Also check - GST Invoice Format – Download Custom Templates for Free 

FAQs on Invoice Numbers

What is the invoice number in a GST bill?

The invoice number in a GST bill is a unique serial number used to identify each invoice. It helps in tracking transactions and is required for GST filing and compliance.

What is the invoice number, and why is it important?

The invoice number is a unique ID for every bill issued. It’s important because it helps maintain proper records, avoid duplication, and ensure GST compliance.

What is the invoice number format for GST?

The invoice number format for GST must be serially numbered, unique for each financial year, and not exceed 16 characters. It can include both letters and numbers.

What is the invoice number, and how to generate it?

The invoice number is a unique code on each bill. You can generate it manually, in Excel, or automatically using GST-compliant software like GimBooks.

What is the invoice number, and where to find it?

The invoice number is usually printed at the top of the invoice or receipt. It is labeled as “Invoice No.” and is used to identify that specific bill