What to put in a business email signature

What the signature is doing

When someone who has never heard of you gets your email, the signature is where they check you're real. A property manager will glance at it to see whether you have a proper business name, a local number and a licence, and a builder may look up your licence before replying. For any email that offers your services, the signature is also where you meet the Spam Act's rule on saying who you are. Our guide to writing a first email to a business covers the email above it, so this one goes through the signature line by line.

The lines a small business signature needs

If you work from home you don't need your street address, because the suburbs you cover tell a buyer more than your own address does. Your role is worth a few words because a facilities manager reads "owner" and "licensed plumber" very differently from a bare name. Leave out the rest: inspirational quotes, award badges, a second mobile and a paragraph of legal disclaimer all push the useful lines further down.

Licence numbers in Queensland and NSW

In Queensland, section 54 of the Queensland Building and Construction Commission Act 1991 says an advertisement a licensee publishes in connection with their business must contain the name under which they are licensed. It must also state that they are licensed under the Act and give the licence number, with a maximum penalty of 35 penalty units. The QBCC's own guidance says licence details must be easily legible and reasonably prominent, that trading names aren't licensed, and that an advertisement showing only a trading name will most likely be non-compliant. Its list of what counts as advertising includes websites, social media, business cards and vehicle signage.

In NSW, Fair Trading's guidance on building trade advertising says the licensee's name and licence number must be shown in all advertising, under the Home Building Act 1989. It asks for the licence number with the correct category of work and a business phone number, and it allows a registered business name in place of the licensee's name. It covers print, internet, television, radio and other advertising.

Neither regulator's list mentions email by name. An email that offers your services to a business is still very hard to argue isn't advertising, so if you hold a QBCC licence or a NSW contractor licence, put the details in your signature exactly as your regulator describes them. In other states, or if your licence comes from a different regulator, ask that regulator whether the same applies before you assume it doesn't.

Where the ABN fits

No rule says every email must show an ABN, but there are good reasons for a small business to put it in the signature. ACMA's guidance on identifying yourself in a marketing email asks for the correct legal name of your business, or your name and your ABN. That matters for a sole trader whose trading name isn't a legal name on its own, because "Jess Morgan, Westside Plumbing (ABN ...)" ties the two together in one line.

Companies have a firmer rule. ASIC says that under section 153 of the Corporations Act a company must show its full name and its ACN (or an ABN that contains it) on documents such as business letterhead, invoices and documents issued for a particular transaction, while business cards and envelopes are exempt. ASIC also says a registered business name holder must include the business name and ABN on business documents such as invoices and purchase orders. A quote sent by email may count as one of those documents, so if your quotes go out from the same signature it makes sense to have the details there already.

There's a money reason too. The ATO says that if a supplier doesn't quote its ABN, the business paying it generally has to withhold the top rate of tax from the payment. An ABN that's already in your signature and on your quote saves that conversation with a new client's accounts team. Business.gov.au also lists the ABN among the details required on every tax invoice.

What the Spam Act asks of a commercial email

Section 17 of the Spam Act 2003 says a commercial email must clearly and accurately identify the person or organisation who authorised it and include accurate information about how to contact them. That information has to be reasonably likely to stay valid for at least 30 days after you send. ACMA adds that if someone else sends messages for you, the email must still identify your business as the one that authorised it. A signature with your business name, ABN and a working phone number covers this.

Section 18 requires a clear and conspicuous statement that the reader can send an unsubscribe message to an address in the email, and that address must be able to receive it for at least 30 days. ACMA's checklist says the request must be honoured within 5 working days and the reader can't be charged or made to log in to an account. Its own example wording is a reply with "unsubscribe" in the subject line, so you don't need a special service. One line under your signature does it.

If you'd rather not hear from me, reply "unsubscribe" and I'll take you off my list.

Ordinary job emails to a customer about their booking aren't the worry here. Any email that offers or promotes your services is, and that includes a follow-up. Most email programs let you save more than one signature, so keep one with the unsubscribe line for emails to businesses you're introducing yourself to. Our guide on whether cold emailing is legal in Australia covers consent and the rest of the Act.

Why a plain text signature arrives better

Be wary of anyone who tells you a precise number of images or links that sends email to junk, because Google and Microsoft don't publish one. What they do say is still worth knowing.

Google's email sender guidelines ask that links in a message be visible and easy to understand, so readers know what to expect when they click. They say sender information should be clear and visible, and they warn that using HTML and CSS to hide content might get a message marked as spam. They also suggest regularly checking that domains linked to yours aren't listed as unsafe on Google Safe Browsing. Every link in your signature is another domain attached to your email, and a row of social media icons, a booking link and a shortened review link add several. One link to your own website, written out in full, keeps it simple.

Images cause a different problem. Microsoft says classic Outlook, including Outlook for Microsoft 365 and Outlook 2016 to 2024, is configured by default to block automatic picture downloads from the internet. If the reader's Outlook is set that way, a signature made as a single picture, with your phone number and licence inside it, won't show until they choose to download pictures. Keep the details as text. A small logo is fine if you want one, but nothing in it should be information the reader needs. Our guide on why business emails go to junk covers authentication and sending volume, which matter far more to delivery than any signature.

A good example

Here's a signature for a made-up Queensland plumbing company. The names and numbers are invented.

Jess Morgan
Owner and licensed plumber
Westside Plumbing Pty Ltd (ABN 00 000 000 000)
Licensed under the QBCC Act, licence no. 0000000
0400 000 000
westsideplumbing.example
Ipswich, Springfield and the Lockyer Valley

If you'd rather not hear from me, reply "unsubscribe" and I'll take you off my list.

It gives the name the company is licensed under next to its ABN, and it states the licence the way section 54 asks. A reader can ring one number, check one website and see straight away whether the business covers their suburb. Everything is text, so it shows the same in Outlook, Gmail and on a phone. A NSW plumber would write the licence line as their contractor licence number with the category of work, as Fair Trading's guidance asks. The unsubscribe line sits under the signature on emails to businesses you're introducing yourself to, and comes off for your everyday job emails. When Curlew writes to businesses in a client's name, every email carries that client's business details and a way to stop.