Use ChatGPT custom instructions to save preferences that belong across your business conversations, such as writing tone, answer format, and how to handle missing facts. Open Settings, then Personalization, enable customization, and add a short set of instructions. Keep customer details, changing prices, and individual jobs in the relevant conversation or project.
Updated September 21, 2026. Product details checked against OpenAI's current documentation.
If every customer reply starts with the same explanation of how you write, saving those preferences removes some repeated setup. The important choice is what to save. A useful default for every conversation is different from a rule that belongs only to your shop's refund process.
Key Takeaways
- Custom instructions hold preferences that should apply across chats; they do not replace the facts needed for a particular job.
- Character limits currently allow 1,500 characters on Free and Go, and 5,000 characters on Plus, Pro, Business, Enterprise, and Education.
- Project instructions keep guidance with a specific area of work. Use the ChatGPT Projects guide when the task needs its own files and rules.
- Human review still matters. A written instruction to ask permission does not replace the product's permission controls.
What are ChatGPT custom instructions?
ChatGPT custom instructions are saved directions about how you want the assistant to respond. OpenAI makes the feature available on all plans across web, desktop, iOS, and Android, according to its custom instructions documentation.
Suppose you run a repair business and use ChatGPT for customer emails, staff checklists, and supplier questions. A warm tone and a rule against inventing dates suit all three tasks. The details of a particular repair do not belong in a setting that also affects tomorrow's supplier conversation.
Save a working preference, not an entire business manual. A longer instruction field gives you more room, but it also gives you more rules to maintain. OpenAI's personalization guide describes custom instructions as preferences to follow across chats, such as response style.
These instructions guide responses; they do not make the assistant accurate or give it access to business systems. If you need it to work with documents and connected services, that is a separate setup covered in the ChatGPT Work guide.
What belongs in custom instructions instead of a project?
Custom instructions suit stable preferences that remain useful across unrelated tasks. A project or individual conversation is a better home for material that applies only to one business activity.
If you run a store, your preference for short paragraphs can travel between a product description and an employee announcement. Your holiday returns policy should stay with the work that needs it. Treat the following table as a scope decision, not a claim that ChatGPT enforces a privacy boundary between these categories.
| Information | Recommended home | Reason |
|---|---|---|
| Preferred tone and paragraph length | Custom instructions | Useful across most conversations |
| Ask before guessing a missing amount | Custom instructions | A broad working preference |
| A specific refund policy and approved examples | Relevant project | Only the customer-service work needs them |
| This week's promotion and its end date | Current task | The information expires |
| A supplier quote or customer order details | Relevant task or approved project | The facts belong to that job |
| Passwords or payment card details | Keep out of instructions | Use the service's secure controls instead |
A project is not permission to upload anything. Use only information you are allowed to share, and check your account's data controls before adding private business records.
How do you set up ChatGPT custom instructions?
Set up custom instructions through ChatGPT's personalization settings, then check the result in a fresh conversation. Allow about ten minutes to prepare a first version, plus time to review the answers it produces.
If you manage bookings for a local service, start with how replies should sound and which facts the assistant must preserve. Leave availability, prices, and individual appointments in the task itself.
- Save your current instructions. Copy any existing text into a private note before changing it. That gives you a way to restore the old version if the new directions cause problems.
- Open the correct settings. On web or desktop, open Settings and select Personalization. On iOS or Android, OpenAI's current help article directs you to Settings, then Customize ChatGPT.
- Enable customization. Turn on Enable customization and enter your directions in the Custom Instructions field. Labels and controls can vary across surfaces, so follow the options your account displays.
- Keep the first version focused. Add preferences you want across tasks. Do not paste your customer list, current price sheet, or a long sequence for one job.
- Start a fresh chat and test. Use an invented customer request without private data. Compare the draft with your instructions before you use it in the business.
OpenAI's help article says settings changes apply immediately across chats, but its history FAQ also says previous versions remain in chat history. Start a new conversation when checking a change, and do not expect edited instructions to rewrite earlier messages.
A reusable custom instructions example for business
A useful starter template sets tone, fact-handling, and review expectations without assuming which business you run. The example below contains 714 characters, including spaces and punctuation, so it fits the documented Free and Go limit.
If you write both customer emails and internal notes, this gives ChatGPT a consistent starting point while leaving the job-specific facts in your request. Review the text before saving it and remove any preference that does not match how you work.
I use ChatGPT to help with small-business work. Write in clear, direct sentences with short paragraphs. Avoid hype, emojis, and invented claims. Put the requested draft or answer first, then add a brief note on anything I need to check. Preserve names, dates, amounts, and commitments from the information I provide. If a missing fact would change the result, ask one focused question rather than guessing. Label assumptions and keep estimates separate from confirmed facts. For customer messages, use a warm, professional tone and avoid promising refunds, discounts, dates, or results I have not authorized. Suggest changes before taking actions that affect other people or business records; wait for my approval.
The approval sentence expresses your preference. It is not a security control. Keep approval requirements enabled in any connected product, and review anything that sends a message, changes a record, or makes a commitment.
A worked scope audit with eight business instructions
This scope audit shows how to separate reusable preferences from temporary information before saving anything. It is a synthetic teaching exercise, not a real business case or a measured ChatGPT result.
Imagine you collected eight notes while preparing an assistant for a small shop and a repair service. The answer key below places each note where its scope makes sense. The counts and template length were checked with a small verification script; the classification itself is editorial judgment.
| Proposed instruction | Decision | Why |
|---|---|---|
| Use clear sentences and short paragraphs. | Keep as a global preference | Applies across different tasks |
| Do not invent prices, dates, or commitments. | Keep as a global preference | Protects factual consistency |
| Show assumptions separately from confirmed facts. | Keep as a global preference | Makes uncertainty easier to review |
| Use this shop refund policy for customer replies. | Put in the relevant project | Applies to one workflow |
| Use this repair quote template for estimates. | Put in the relevant project | Applies to one output type |
| The weekend promotion ends on September 27. | Put in the current task | A dated campaign detail |
| This supplier quote expires on Friday. | Put in the current task | A temporary purchasing fact |
| Use the customer payment card number. | Exclude | Sensitive payment data does not belong here |
The result is three global preferences, two project-level directions, two task details, and one excluded item. Download the scope audit and complete starter template to inspect the source material and character count.
No ChatGPT model was tested for this exercise, and no account settings were changed. The exercise checks the input's scope and size, not whether a model will obey it. The next step supplies that missing check on your own account.
How do you check whether the instructions help?
Check custom instructions with several different tasks, including one that should not inherit your business-specific wording. Judge the output you receive rather than asking ChatGPT whether it followed the rules.
For example, use a fictional delivery question, a staff closing checklist, and a personal packing list. A salesy sign-off in the packing list is a useful warning that a rule is too broad.
- Customer email: Supply an invented order delay without a replacement date. Check that the draft does not promise a date or refund you never supplied.
- Staff checklist: Provide the actual steps you want rewritten. Check that ChatGPT preserves their order and does not add a task you never approved.
- Unrelated request: Ask for a packing list. Check that the answer does not drag in your business, product descriptions, or customer-service rules.
Save the same test requests with the instruction text. After an edit, rerun them in new chats and compare factual preservation, useful format, and unwanted spillover. One good answer is evidence about that answer, not a guarantee about the next task.
How do you fix instructions that cause problems?
Fix a troublesome instruction by making its scope clearer, moving it closer to the relevant task, or removing it. Adding more directions before finding the conflict can make the problem harder to diagnose.
If a restaurant announcement keeps sounding like a customer apology, look for a global customer-service rule. Change “always apologize first” to a task-specific request, then repeat the same announcement test.
Keep a dated copy of each version you try. To disable custom instructions, return to the personalization settings and turn Enable customization off; OpenAI also documents deleting the saved text as an optional step. Disabling the feature does not erase earlier messages or undo anything already sent.
Frequently Asked Questions
Custom instructions affect response preferences, while the task still needs current facts and human review. These answers cover the main setup decisions for a business account.
Are ChatGPT custom instructions free?
Yes. OpenAI lists custom instructions as available on all plans. Its current help article gives Free and Go users 1,500 characters, and Plus, Pro, Business, Enterprise, and Education users 5,000 characters. Check the limit shown in your account if the interface differs.
Should I put customer details in custom instructions?
Keep customer-specific details with the approved task that needs them, rather than in global instructions. Share only information you have permission to use. OpenAI warns that relevant instruction information may reach third-party plugin developers, so a global field is a poor place for confidential records.
Are custom instructions the same as memory?
No. OpenAI describes custom instructions as preferences you provide across chats, while memories can carry context forward from earlier conversations. Review both when troubleshooting an unwanted response. Changing one setting does not mean you changed all the context the assistant can use.
Will custom instructions make ChatGPT stop guessing?
They can tell ChatGPT how you want uncertainty handled, but they do not guarantee factual accuracy. Give it the necessary source facts, check amounts and dates yourself, and test cases where information is missing. Reject a confident answer that invents a commitment.
Can I use the template for more than one business?
Yes, if its preferences genuinely apply to both. Keep each business's policies, prices, customer records, and job-specific templates with its own work. A broad preference for concise answers can be shared; a restaurant refund policy should not become the default for a repair estimate.
Build one repeatable habit
A useful instruction set gives you a starting point you can inspect and revise. Choose one recurring task, save only its broadly useful preferences, and keep a short test you can repeat after changes.
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About the Author
Thomas Echezabal helps small business owners automate their busywork with AI and get real hours back each week. He has worked with small businesses his entire career, including 200+ clients on Fiverr.
