A One-Page Brand Voice Guide for When Your Team Writes With AI

Short answer: Write one page that covers who you're talking to, three voice traits with examples, how your tone shifts by situation, words to use and avoid, formatting and spelling rules, and the facts that must never come from the AI. Paste a condensed version into your AI tool's instructions so every draft starts from it. Then keep a human review step, because the guide shapes the style but can't stop a tool inventing a price or a promise.

Why a small team needs this now

When three people write your social posts, emails and website updates with an AI assistant, you get three different voices plus the assistant's own default, which tends towards polite, generic marketing language. Customers notice when your Instagram sounds like a bank and your emails sound like a teenager.

Big brands have long style guides. You need one page that people actually read and that fits into an AI tool's instruction box. Mailchimp's public content style guide is a useful model for the core idea: your voice stays the same all the time, while your tone changes with the situation and the reader's mood.

Below is the template, section by section, with an example for a hypothetical bike repair shop in Bristol.

The template, section by section

Section 1: Who we're writing for

Two or three sentences on your customers and what they want from you.

Example: Commuters and weekend riders around Bristol who want their bike fixed quickly and explained simply. Many aren't mechanics and feel talked down to at other shops.

Section 2: Our voice in three traits

Pick three adjectives, and for each write "this, not that" plus a short sample. The "not that" matters more than the adjective; everyone thinks they're "friendly".

Example:

Straightforward, not technical. "Your brake pads are worn and need replacing" not "Pad compound has degraded beyond spec."

Warm, not jokey. A light touch is fine; puns in every post aren't.

Confident, not pushy. We recommend; we don't pressure.

Mailchimp's guide does something similar, describing its voice as plainspoken and genuine and explaining what each means in practice.

Section 3: How our tone shifts

List four or five common situations and how the tone changes.

Situation	Tone
Social post about a new service	Upbeat, short, one clear call to action
Reply to a complaint	Calm, specific, apologise once, explain the fix
Booking confirmation email	Clear and brief; dates and times first
Website service page	Practical and reassuring; answer common questions
Price increase notice	Plain and honest; reason in one sentence, no spin

Section 4: Words we use and words we avoid

Two short lists. GOV.UK's A to Z style guide includes a "Words to avoid" list (for example, "collaborate" becomes "work with", and "deliver" is reserved for real things like post and services). Your list can work the same way.

Example:

Use: service, fix, check, bike, quote, book.

Avoid: solutions, world-class, cutting-edge, passionate about, "reach out", "game" metaphors.

Our names for things: "full service" (never "overhaul"), "collection and delivery" (never "concierge").

Section 5: Formatting and spelling

Decisions people otherwise make differently every time:

Example: British spelling. Sentence case for headings. Prices with the pound sign and no pence for whole amounts (£45). Dates as "Tuesday 3 March". No more than one emoji per post, never in emails. Bullet points for lists of three or more.

Section 6: Facts the AI must never supply

This is the section most voice guides forget, and the one that matters most with AI. List everything that must come from a person or a source document, never from the tool:

Example: prices, opening hours, turnaround times, guarantees and warranties, discounts and their end dates, customer quotes and reviews, statistics, staff names, anything about safety.

Add one line for the AI instruction: "If you need one of these facts and it isn't in my message, leave a placeholder like [PRICE] instead of guessing."

Section 7: Two short examples

One paragraph that sounds right, and the same paragraph written badly. Examples teach tone faster than adjectives do.

Right: "Gears slipping? Bring it in before 10 and we'll usually have it back to you the same day. We'll call before doing anything that costs more than the quote."

Wrong: "Experience a world-class gear-tuning solution delivered by our passionate team of cycling experts."

Section 8: The review step

Who checks AI-assisted content before it's published, and what they check: facts in Section 6, tone against Section 3, and spelling against Section 5. For a small team, the rule can be as simple as "nobody publishes their own AI-assisted text without a second person reading it."

Turning the guide into AI instructions

Your one-page guide is for people. For the AI tool, condense it to a short block of instructions: audience, three voice traits with their "not that", spelling, words to avoid, and the placeholder rule from Section 6.

Most assistants have somewhere to store this so you don't paste it every time:

Microsoft Copilot: Microsoft's support pages describe custom instructions in Copilot settings for how Copilot responds to you, and separate instructions for a Copilot Notebook. Microsoft's own example for notebook instructions includes tone, formatting and how a client's name should be written, which is exactly the kind of detail a voice guide holds. Shared notebooks let others see and edit the instructions.
Other assistants, including ChatGPT: most offer custom or project-level instructions. Check the provider's current help pages for where these live, because menus change often.

Two practical tips:

Keep the instructions short. A long instruction block tends to be followed loosely. Put the full guide in a shared document and the essentials in the tool.
Test it. Ask the tool to write a post, a complaint reply and a booking email. Compare them against Section 7. Adjust the instructions, not just the drafts.

Keeping the guide alive

Review it twice a year or when something changes: a new service, a rebrand, a new person writing. Add any word that keeps causing problems to the avoid list. Keep the guide where everyone writes, and link it in your team's onboarding notes.

FAQ

How long should a brand voice guide be?

For a small business, one page for people and a short paragraph for the AI tool. Longer guides get skimmed.

Will the AI follow the instructions every time?

Not reliably. Instructions improve consistency, but drafts still need a human read, especially for facts and promises.

Should we tell customers we use AI to write?

That's a business choice, and rules can differ by sector and country, so check what applies to you. What matters most is that every published fact is checked and the voice sounds like your business.

If you'd like a one-page voice guide written with you and set up as instructions in the tools your team already uses, tell us who writes your content today.