We’ve all been there—filing tax documents, applying for a business loan, or trying to issue an invoice, and suddenly you can’t find your ABN number. It’s frustrating, but it is also highly prevalent, particularly among Australian sole traders and small business owners.

Your Australian Business Number (ABN) is essential for your business identity, tax obligations, and communications with the Australian Taxation Office (ATO). So, what happens if you’ve lost it?

This simple guide will help you find the lost ABN quickly, recover it step-by-step, and protect it in the future using tools like the ABN lookup tool, along with updated tips for 2025.

What Is an ABN and Why Does It Matter?

The Australian Business Register (ABR) issues an 11-digit unique identification number known as an ABN (Australian Business Number). It links your business with the ATO and is mandatory for:

Issuing invoices
Registering for GST
Filing BAS and tax returns
Claiming business deductions
Opening business bank accounts

Without an active ABN, you may face challenges like withheld payments or being unable to claim tax credits. That’s why it’s important to find the lost ABN as soon as possible. However, losing your ABN doesn’t mean you’ve lost your business registration—it simply means you need to recover it. And that’s where we come in.

How Can I Find the Lost ABN Number?

If you’re wondering, ‘I lost my ABN, where can I find my ABN?’—you’re not alone. Many business owners face this challenge at some point. The good news is, there are several reliable ways to find the lost ABN quickly and easily. Below, we’ll guide you through five effective and 100% legitimate methods to recover your ABN.

1. Use the Official ABN Lookup Tool

This is the fastest and easiest method to find the lost ABN.

To get started, visit the official ABN Lookup Tool, which is managed by the Australian Business Register (ABR). Here are the simple steps to follow:

Visit the ABN Lookup website: Go to ABN Lookup Tool.
Enter your business name or trading name: You can also search using your full legal name.
Browse the results: Once you submit your search, you’ll see a list of businesses that match your query.
Find your ABN: Your ABN, along with the business status, entity type, and GST registration, will be displayed. This is especially helpful for verifying if your ABN is active or cancelled.

The ABN search Australia-wide is free, easy to use, and accessible 24/7. It’s a reliable tool to help you find the lost ABN with minimal hassle.

Tip from ISM: Always download or screenshot the result for future reference to ensure you have your ABN on hand whenever needed.

2. Check Emails and Documents for Your ABN

Still can’t find the lost ABN? You might already have it saved somewhere without realising it. Before you go any further, take a moment to check the following places:

Business registration emails from the ATO or ABR
Invoice templates you’ve used for past transactions
Accounting software like Xero or MYOB (ABNs are often stored here for reference)
Business bank account documents (your ABN might be on file)
Business Activity Statements (BAS) (ABNs are often found in the footer)

You’d be surprised how often people find the lost ABN from the footer of an old invoice or BAS document. If you keep your business records organised, you might quickly recover your ABN without the need for further steps.

Need help sorting your business paperwork? At ISM Accountant, our bookkeeping services make it simpler to maintain organization and monitor your company’s data.

3. Use MyGov and ATO Online Services

If you’re registered as a sole trader, your MyGov account might have your ABN stored. This is one of the easiest ways to find the lost ABN if you can’t access external documents or emails. Here’s how to check:

Log in to MyGov: Access your account by visiting their website.
Link your account with the ATO: If you haven’t already linked your MyGov account with the Australian Taxation Office (ATO), you’ll need to do that first.
Click “Business” or “Profile”: Once linked, go to the “Business” section (or “Profile” section if you’re accessing your details).
Check the “Business Details” or “Business Registrations” section: Here, you’ll find information related to your ABN and business registration details.

This method is especially helpful for sole traders who may have difficulty locating external paperwork. By using MyGov and ATO Online Services, you can quickly find the lost ABN Australia-wide.

Recommended Read: Common reasons for ABN delay

4. Contact the ATO or ABR Directly

If online methods fail, you can always contact the ATO or ABR support directly to find the lost ABN. Here’s how you can reach them:

ABR support line: 13 92 26
ATO business line: 13 28 66

When you call, have the following details ready to verify your identity:

Your full legal name
TFN (Tax File Number) if you are a sole trader
Your business name or entity name
Your date of birth or the business start date

Your ABN can be given to you by phone or email by the ATO or ABR when your identity has been verified. This is an efficient way to find the lost ABN if other methods haven’t worked.

Need help retrieving your ABN quickly? At ISM Accountants, we assist clients in recovering their ABN without the wait or stress. Reach out to us today, and we’ll make the process seamless for you.

Was Your ABN Cancelled? Here’s How to Reactivate It.

Sometimes, when trying to find the lost ABN, business owners discover that their ABN has been cancelled, usually due to inactivity, outdated information, or because the business was reported as closed.

How to Check if Your ABN Was Cancelled?

Visit the official ABN Lookup Tool
Type in your full name, business name, or past ABN (if you remember it)
Check the ABN status shown on the results page

If it says “Cancelled”, this means the Australian Business Register has deactivated it, often due to:

No recent business activity
Not lodging tax returns or BAS
Incorrect or missing business details
The business is no longer operating.

Recommended Read: When should you cancel your ABN?

Can You Reactivate a Cancelled ABN?

Technically, no—you cannot “reactivate” a cancelled ABN.
You must reapply for a new ABN with the exact business details (if your business is still operating).

How to reapply:

Visit the ABR Site.
Select “Apply for an ABN”
Use your existing business details and explain that it’s a continuation of your previous business
Submit updated info like business activity, structure, and contact details

The ATO or ABR may reference your old ABN, but you’ll be issued a new ABN if your application is approved. ISM can help you set up an ABN for you.

How to Replace Your ABN Certificate?

If you’ve misplaced your ABN registration certificate, don’t worry—getting a new one is easy. Many business owners looking to find the lost ABN also need to replace their ABN certificate for tax, banking, or compliance purposes.

Here’s how to replace your ABN certificate:

Go to the official ABN Lookup Tool
Search for your business name or your ABN (if you remember it)
Once your listing appears, you’ll see:
- ABN status
- GST registration
- Entity type
Click “Print” or “Download” to create a PDF or physical version of your ABN registration

While this isn’t a formal “certificate” issued by the ABR, it functions as proof of your ABN and is accepted by banks, clients, and regulatory bodies.

Need an Official-Looking ABN Document?

For more formal use, like legal compliance, grant applications, or tax registration, you might want a custom certificate that includes:

Your ABN
Business name
Entity type
Date of registration
GST status
Legal structure

At ISM Accountants, we can help you generate an official document tailored to your needs—accurate, professional, and ready to submit wherever needed. Need help? Explore our best tax-related services.

How to Keep Your ABN Safe for the Future?

After going through the hassle of finding the lost ABN, it’s smart to make sure you never lose it again. Your Australian Business Number is vital for invoicing, tax reporting, and business identity, so keeping it safe is key.

Here’s how to protect your ABN going forward:

Save your ABN in secure cloud platforms like Google Drive, Dropbox, or OneDrive.
Email it to yourself or store it in a locked folder within your email drafts for easy access.
Add it to all invoice templates, contracts, and your business plan documents.
Link your ABN to your MyGov profile, especially if you’re a sole trader using ATO Online Services.
Use cloud accounting software (like Xero, MYOB, or QuickBooks), which securely stores your ABN and business information.
Let your accountant manage all ABN registrations, renewals, and tax documents.

Pro Tip from ISM Accountants: Losing your ABN doesn’t mean losing your business, but staying organised helps avoid unnecessary delays. If you ever need to find your lost ABN again, having it stored in multiple places will save time and stress.

Why Choose ISM Accountants to Help You Recover an ABN?

When you need to find the lost ABN fast and accurately, ISM Accountants is the professional team you can trust. As a leading Australian tax agency, we go beyond basic bookkeeping—we provide comprehensive business support tailored to your needs.

Find lost ABN quickly and securely
Register or reactivate ABNs
Replace ABN certificates
Lodge BAS & tax returns
Handle ATO correspondence on your behalf

ISM Accountants supports businesses across Australia from Melbourne to Sydney, Brisbane, and beyond. Whether you’re just starting or managing a growing operation, we’ll make sure you’re compliant, organised, and stress-free.

Recommended Read: What is the difference between an ABN and an ACN

Conclusion

Don’t Let a Lost ABN Disrupt Your Business—Recover It with Confidence
Losing your ABN might feel overwhelming, but with the right steps, it’s easy to find and recover. From using official ABN lookup tools to accessing MyGov or contacting the ATO, there are several secure ways to retrieve your business number. If your ABN has been cancelled, you can still reapply and get back on track.

At ISM Accountants, we simplify this process for you. Whether you’ve lost your ABN, need a new certificate, or want help re-registering your business, our expert team is here to make it stress-free and fast. We support businesses across Melbourne, Sydney, Brisbane, and all of Australia, ensuring your business stays compliant and organised.

Need help finding Contact ISM Accountants, and So that you can concentrate on managing your company, let us handle the paperwork.