AI writing sands off the Australian register first

The first thing AI assistance takes out of your copy is not accuracy. It is register. Research presented at CHI 2025 found that AI writing suggestions homogenise output toward a Western default and strip cultural nuance, and for an Australian business that shows up as a slow drift toward sounding like an American company that opened a Sydney office.

That matters more than it sounds. Factual errors get caught, because someone eventually checks. Register drift does not get caught, because every individual sentence is fine.

The specific tells

Generic advice about brand voice is worthless here. These are the concrete things that appear in Australian marketing copy after a model has been involved, in rough order of frequency.

Spelling drift. The American forms of colour, centre, behaviour, defence, analyse and optimise creep back in one sentence at a time. Models default to those forms and will reintroduce them in the sentences they rewrite even when the rest of the document is correct. This one is easy to catch and still ships constantly.

American corporate idiom. The reaching-out, the touching-base, the circling-back, the going-forward, every superlative that ends in class. None of these are wrong exactly. All of them read as imported.

Wrong regulators and institutions. The US trade regulator instead of the ACCC. US health privacy law instead of the Privacy Act. The US labour department instead of Fair Work. The US drug regulator instead of the TGA. This one is not a style problem, it is a credibility problem, and it appears in compliance-adjacent copy constantly.

Wrong units and formats. Dates rendered month-first. Dollar figures that do not state AUD in a document that will be read by overseas buyers. Imperial measurements. Zip code instead of postcode, cell instead of mobile.

Wrong geography. Examples set in Ohio. References to Main Street. Seasons inverted, so a spring campaign lands in September copy written for a March launch.

Register inflation. Australian business writing is flatter and drier than American business writing. Models push toward enthusiasm, so every product becomes a breakthrough, every process becomes effortless and every tool becomes the newest thing on the market. An Australian reader discounts all of it instantly, which means the sentence carrying the actual claim gets discounted with it.

The dash. Models insert long dashes at a rate no human writer does. It has become one of the fastest visual tells that a document was machine-drafted.

Why proofreading does not catch it

Proofreading checks whether the sentence is correct. Every drifted sentence is correct. A sentence that opens by saying the team is excited to reach out about a solution contains no error.

The failure is only visible against a baseline, and the baseline lives in the head of whoever knows how the company actually talks. If that person is not in the loop, the drift compounds quarter over quarter until the brand voice document describes a company that no longer exists in the copy.

The measurable version: take a piece your founder wrote in 2023 and a piece your team published last month. Read both aloud. If the second one sounds like it came from a different company, you have the problem.

The fix that works

A brand voice document full of adjectives does not fix this. Confident but approachable is unenforceable and every team has one.

What works is a sample bank and a ban list.

The sample bank is 15 to 20 pieces of your real copy that everyone agrees sounds right. Not aspirational examples from other companies. Your own. Every new piece gets read against them before it ships, by a person, out loud.

The ban list is specific and boring. Every American spelling variant you keep seeing. Every imported idiom. Every institution name that gets substituted. Every superlative your reader would discount. Put it in a file, run it as a find-and-replace check, and add to it every time something slips through.

Then three habits:

1. 1.Read aloud, always. Register problems are audible and invisible. This single habit catches more than any tool.
2. 2.Localise the examples deliberately. If a piece uses an example, it should be a Sydney or Brisbane or Perth example with a real detail in it, because the specific local reference is the thing a model cannot generate and the thing an Australian reader trusts.
3. 3.Have one person own voice. Not a committee. One named person whose sign-off is required on anything customer-facing, chosen because they can hear the difference.

The part that is genuinely hard

Some drift is not fixable with a list, because it is structural rather than lexical.

Australian business writing tends to state the thing and stop. American business writing tends to state the thing, restate it as a benefit, and then close with a line about what it means for you. Models are trained overwhelmingly on the second pattern and will rebuild it even after you have removed every flagged phrase.

The only reliable counter is cutting. When a model drafts three sentences where one would do, the first two are usually the imported structure and the third is the point. Delete forward until you hit the sentence that carries information.

The commercial reason to care

An Australian buyer at a medium or large business reads a lot of imported marketing. Sounding local is one of the few remaining fast signals that you understand the market they operate in, the regulator they answer to, and the way business gets done here.

It is also nearly free to protect and expensive to rebuild once a year of copy has drifted.

Read it aloud, and if it does not sound like your company, it is not your company's copy.