Use AI at your Australian tax practice without exposing TFNs

AI for accountants rarely sees a whole return. It sees the slice that is giving trouble: a BAS reconciliation that is out by the GST on one invoice, a single touch payroll event the ATO has rejected, the query list for an SMSF audit, or trust distribution minutes that need tidying before 30 June.

Each slice has its own numbers. Payroll brings the employee’s TFN, date of birth, super fund USI and bank details. The BAS brings ABNs and the client’s account. An SMSF file carries members’ TFNs and, sometimes, a Centrelink CRN where a member also receives a pension. A rental schedule still carries the client’s date of birth and the refund BSB.

Nonimo picks those identifiers out of the selected text and puts placeholders in their place on that computer, before anything is sent. What the Privacy Act adds on top is covered in our guide to choosing a chatbot under the Privacy Act.

The invented pay event below is the kind of thing a bookkeeper pastes on a Friday: the fund changed, and the year to date gross went to the ATO as zero. Select it, press one key, and the employer’s name, the employee’s name, TFN, date of birth, USI, BSB and account number leave as placeholders.

The figures stay, and so does the question. The model can still reason about the gross, the PAYG withheld and the super guarantee, because none of those identifies anyone. Each placeholder is numbered, so [PERSON_1] and [COMPANY_1] stay distinct if the answer refers to both.

The reply comes back written around the placeholders, and the real details return on your own screen. Every change is marked before you paste, and one click puts back a detail you do want sent. More on our security page.

Tax and BAS agents now have their own TPB guidance on AI. Issued on 22 July 2026, TPB(GS) 55/2026 reads Code item 6 across to AI tools: client information is not to go to a third party without the client’s permission, and an AI tool can be that third party, depending on how it is configured and used.

The statement also recommends telling the client to whom and where a disclosure will be made, where data will be stored and whether AI tools may be used. That conversation fits naturally into a signed engagement letter. Where TFNs are involved, it says, “additional obligations under the Privacy (Tax File Number) Rule 2015 will apply”.

The permission question turns on what you enter, and what you enter is the part Nonimo changes. Under Competency the TPB adds that practitioners should verify and review AI generated content and document those steps, with sections 30 and 40 of the Determination behind it. That record of checking stays with the practice.

TPB(GS) 55/2026 did not arrive on a blank page. TPB(GS) 31/2018, on outsourcing and offshoring, was last updated on 30 April 2026. It counts a provider that hosts and runs computing for the practice in a cloud outside Australia as offshoring, and it wants the client’s permission, by engagement letter, signed consent or other communication, before client information goes to that provider. The TPB has not applied it to AI by name, but most of the large AI providers process prompts outside Australia, and a practice reading the two statements together will reach the same place.

TPB(GS) 36/2021 is narrower and older: how a practice should handle TFNs in email. It treats a careless TFN disclosure as a Code item 6 problem as well as a TFN Rule one, strongly recommends the client’s prior specific written authority before TFN information goes out by email, and notes the offence provisions in the Taxation Administration Act 1953 on unauthorised use or disclosure of a TFN. Among the measures it suggests is software that redacts TFNs within documents. A chat window is a less controlled recipient than any client’s inbox.

Nonimo deals with the TFN before either question arises. It becomes [TFN_1], which tells the model what kind of number stood there without giving it away. Our TFN guide shows where the number tends to hide.

Payroll and BAS are usually first, because that is where staff already ask ChatGPT or Copilot for help. Install Nonimo on Mac or Windows from the top of this page and press the key on the next query before it is pasted.

Each computer installs it on its own, with no IT provider booked.

For the whole practice, IT pushes out the browser extension by policy and it covers text in the AI tools without anyone pressing a key. Write to hello@nonimo.ai to set that up. What OpenAI keeps of a paste is in does ChatGPT save your data, and our AI acceptable use policy template has a clause on client permission.