Services
Explore
Free AI assessmentAnswer 15 questions about one process and see where AI could help.
Start an assessmentHow do I train ChatGPT on my business documents?
Set up a custom GPT, a Project or custom instructions with your documents and tone of voice. None of the three methods needs code, and none of them retrains the underlying model.
How To
How To
A step-by-step guide for business owners: write instructions, add your documents to a custom GPT and test the answers before anyone relies on them.
A ChatGPT plan that includes custom GPTs, approved by your business for this use
Brand voice guide or tone of voice document
Product or service description document
FAQ or knowledge base document
Sign in to ChatGPT, open the GPTs area from the menu and choose the option to create a GPT. Menu names change from time to time, so follow the current layout.
In the Create tab, describe what your GPT should do. Include your business name, what it helps with and the tone it should use.
Open the Configure tab. In the Instructions field, describe your business, your tone of voice, what the GPT should help with and any boundaries, for example that pricing questions go to a person.
Under Knowledge, upload the business documents your business has approved for this setup. Text-based PDF, Word and plain text files are the most reliable. Check OpenAI's current help pages for file limits.
Use the Preview panel to ask the questions you expect people to ask. Check that answers are accurate, in the right tone and free of details that are not in your documents.
Save the GPT and choose who can use it from the sharing options your plan offers. For business documents, keep access to the people who need it.
A note on "training"
Training Note
"Training ChatGPT on your business" does not retrain the AI model. Changing the model itself would need a dataset, training infrastructure and machine-learning engineering. The methods in this guide configure an assistant: you give it instructions and reference documents, and it draws on them when it answers. The underlying model stays the same.
There are three ways to do this. Custom GPTs take the most setup and keep a set of reference documents alongside your instructions. Projects group conversations about one area of work with shared files. Custom instructions add standing context to your chats with no files at all. This guide covers them in that order.
You do not need to be technical. You need a ChatGPT plan that includes the method you choose, approval from your business to use it for this work, and your documents in a readable format.
What you need
Documents that work well, and ones to handle carefully
You can start small. Two or three well-written documents, such as a brand voice guide, a service description and an FAQ, give the assistant enough context to produce more relevant drafts than a chat with no background.
Works well
Shows the GPT how you write and what language to use
Gives the GPT current detail to refer to
Gives it agreed answers to common questions
Shows how you describe your work and its value
Helps the GPT follow your usual communication style
Lets the GPT walk through your standard procedures
Lets it answer pricing questions from your published figures
Avoid or handle carefully
Image-only scans may not be read reliably. Use a text version.
Split them by topic so each part is easier to check and update
Keep personal data out of a GPT others can open and out of any setup your business has not approved
Keep internal financials out of a shared tool
Uploading NDA-covered material to an outside service may breach the agreement
Complex table structures often read poorly and cause errors
Step-by-step setup
Three methods, from most setup to least
Method 1 takes the most setup and gives you the most control over what the assistant works from. Method 3 is the quickest to try. Menu names in ChatGPT change from time to time, so follow the current layout if a label differs.
Number1
TagMost setup, most control
Best forRepeated use by you or your team on the same kinds of task
NeedsA paid ChatGPT plan that includes custom GPTs. Check OpenAI's current plans.
- Open the custom GPT builder Sign in to ChatGPT and open the GPTs area from the menu. Choose the option to create a GPT.
- Describe your GPT in plain English The Create tab opens a chat with the GPT builder. Tell it your business name, what the GPT should help with and the tone it should use. For example: "Build a GPT for [Your business], a bookkeeping firm. It should help write client emails, proposals and social posts in our voice: professional, friendly and direct."
- Switch to Configure and write your instructions Open the Configure tab. The Instructions field matters most, because it is where you write a detailed brief. Include what your business does, your tone and style, what the GPT should and should not do, and any specific rules, for example "For pricing questions, suggest booking a call and do not quote a price."
- Upload your knowledge documents Under Knowledge, upload the documents your business has approved for this setup, such as your brand guide, product descriptions, FAQ and past proposals. Text-based PDF, Word (.docx) and plain text (.txt) files are the most reliable. Check OpenAI's current help pages for limits on file numbers and sizes.
- Test it with real questions The Preview panel shows your GPT as others will see it. Ask the questions you expect clients or your team to ask. Check whether the answers are accurate, whether the tone matches your brand, and whether it adds anything that is not in your documents.
- Save and choose your sharing setting Save the GPT and choose who can use it from the options your plan offers. Keep access to the people who need it, and keep a GPT that holds internal documents private to your business.
TipWrite your instructions as if briefing a new employee who follows instructions well but knows nothing about your business. Specific instructions produce more useful drafts.
Number2
TagFiles for one area of work
Best forOngoing work in one area, for example a project for client proposals
NeedsA ChatGPT plan that includes Projects. Check OpenAI's current plans.
- Create a new Project In the ChatGPT sidebar, find Projects and create a new one. Name it after the work area, for example "Client proposals" or "Marketing content".
- Add files to the project Inside the project, add the documents your business has approved for it. Conversations within the project can refer to these files, so you do not need to upload them each time.
- Set custom instructions for the project Projects can hold their own instructions, separate from your general custom instructions. Add a short brief for how conversations in this project should behave.
- Start conversations within the project New chats started inside the project can use the files and instructions you have set. The project sidebar lists earlier conversations in that project.
TipProjects give a set of conversations access to your documents with less setup than a custom GPT. If others need access, check the sharing options your plan currently offers.
Number3
TagQuickest to set up
Best forStanding context in your chats without file uploads, such as your tone and key business facts
NeedsA ChatGPT account with personalisation settings
- Open Custom Instructions Open your profile menu in ChatGPT and choose the personalisation or custom instructions option. This opens the fields where you add standing context.
- Describe your business Add a short description of your business: what you do, who you serve, your tone of voice and any standing preferences. ChatGPT takes this into account in new conversations.
- Describe how it should respond Describe how you want ChatGPT to respond: format, level of detail, whether to ask clarifying questions and what to avoid. For example: "Use plain English. No bullet points unless I ask. Suggest a next action at the end."
- Save and test Save your changes. Start a new conversation, ask it to write something in your brand voice and check whether the result follows your instructions without further prompting.
TipCustom instructions hold text, with no documents attached, and each field has a character limit. Paste the most important parts of your brand guide straight into the field.
Keeping it updated
Your GPT only knows what you last gave it
A custom GPT works from the documents as they were when you uploaded them. It will not know about changes to your pricing, services or brand until you update it. These are the moments to review your setup.
When your services or pricing change
When your brand voice changes
At a regular review
When you notice wrong answers
When you add new products or services
Privacy notes
What to upload, and what to keep out
Documents you upload are stored by OpenAI. How they are handled, including whether they may be used to improve models, depends on the plan. Consumer plans, business plans and the API have different terms. Check OpenAI's current terms for your plan, and upload only to a setup your business has approved for that data.
| Plan | Training | DPA | Recommendation |
|---|---|---|---|
| ChatGPT Free | Consumer plan. Conversations may be used to improve models, depending on your data settings. | Check OpenAI's current terms | Keep confidential business documents off unless your business has approved this setup for them |
| ChatGPT Plus (individual) | Consumer plan. The data controls in Settings affect whether conversations may be used to improve models. | Check OpenAI's current terms | Check the data controls and get approval from your business before uploading business documents |
| ChatGPT Team | Business plan with separate terms. Check how they treat your files and conversations. | Check the current business terms | Use for business documents your business has approved for this plan. Keep personal client data out unless it is approved. |
| ChatGPT Enterprise | Business plan with its own contract terms. Check how they treat your data. | Check the current contract terms | Agree the approved uses with whoever is responsible for data protection. Take legal advice in regulated sectors. |
Common questions
FAQs
Do I need to be technical to set up a custom GPT?
No. The custom GPT builder works through a chat. You describe what you want the GPT to do in plain English, and it helps set itself up. The main tasks are writing a description of your business and what the GPT should help with, uploading your documents, and testing whether the output sounds right. None of this needs code. The harder part is deciding which documents are approved for the setup and checking the answers.
What's the difference between a custom GPT and pasting my documents into a chat?
A custom GPT keeps your documents and instructions available, so each new conversation with it can draw on them without you pasting anything. Documents pasted into an ordinary chat apply to that conversation only. A custom GPT also holds standing instructions about your brand voice and behaviour. In practice, a custom GPT is set up once and used repeatedly, while pasting documents suits a one-off task.
Which ChatGPT plan do I need?
Creating custom GPTs needs a paid ChatGPT plan. Business plans add options for sharing within your organisation and have different data terms from consumer plans. Plans, prices and features change, so check OpenAI's current plan pages, and choose a plan your business has approved for the documents you intend to use.
What types of documents work best?
Text-based documents in common formats work best: PDF, Word (.docx) and plain text (.txt). The GPT reads the text, so clear, well-structured writing gives better results than complex tables or image-heavy files. Good examples are brand voice guides, product and service descriptions, FAQ documents, past proposals, sample emails in your tone and standard process documents. Scanned PDFs, large spreadsheets with complex formatting and very long documents tend to work poorly.
Will ChatGPT give wrong answers based on my documents?
It can, particularly if your documents are ambiguous or contradict each other. ChatGPT interprets what it reads and can misread a detail or fill a gap with a plausible answer that is wrong. Before using it for anything client-facing, test it with questions you know the answers to. Keep your documents clear and current, and have a person check outputs before they are used outside the business. Treat it as a well-briefed assistant that sometimes gets details wrong.
Can I share my custom GPT with clients or the public?
Custom GPTs can be shared, and the options depend on your plan. Check the current sharing settings before deciding. If anyone outside your business will use the GPT, assume it may repeat anything in its documents or instructions. Keep internal pricing, confidential client information and anything you would not publish out of a GPT that others can open.
Talk to us
We can set up an assistant around your documents and connect it to your systems
Send us the documents you want an assistant to use and the questions it should answer. We look at which setup suits the work, what data can go into it under your approved-use rules, and whether connecting it to your other systems would help.