The short answer: if your business runs on Microsoft 365 and most of the work you want help with sits in Outlook, Teams, Word, Excel and SharePoint, start with Copilot. Copilot Chat costs nothing extra on eligible plans, and the paid Microsoft 365 Copilot licence works inside the emails and files your staff already have. If your team needs a strong general assistant for research, writing and analysis, and your work is spread across several systems, ChatGPT Business is usually the better fit. Some firms are better off with both.
The two products overlap more every month. ChatGPT now connects to Microsoft 365, and Copilot now lets you choose between models. So the useful question isn't which AI is cleverer. It's where your work lives, what your staff will actually use it for, and what you're allowed to put into it.
Prices below are as of October 2026, taken from Microsoft's and OpenAI's UK pricing pages on 24 October 2026. Microsoft's prices exclude VAT.
What you're actually comparing
"Copilot" covers several things, which is where most of the confusion starts.
Copilot Chat is the AI chat included at no extra cost for users with an eligible Microsoft 365 subscription. It answers from the web, comes with Microsoft's enterprise data protection, and can run agents your organisation builds, billed by use.
Microsoft 365 Copilot is the paid licence. It puts Copilot inside Word, Excel, PowerPoint, Outlook and Teams, grounds its answers in your work data (emails, files, meetings and chats), and adds Microsoft's own agents such as Researcher and Analyst. Smaller firms buy it as Microsoft 365 Copilot Business. Larger ones buy the enterprise add-on.
On the OpenAI side, the business options are ChatGPT Business, which was called ChatGPT Team until August 2025, and ChatGPT Enterprise. Both are separate from the Free, Plus and Pro accounts your staff may already be using on their own.
Plans and prices in pounds
| Plan | Price per user a month | Best for | Worth knowing |
|---|---|---|---|
| Copilot Chat | No extra cost | Anyone on an eligible Microsoft 365 plan | Web-grounded chat with enterprise data protection; agents billed by use |
| Microsoft 365 Copilot Business | £16.10 paid yearly (£13.80 for the first year if bought by 31 Dec 2026); £19.32 paid monthly | Firms on Microsoft 365 Business plans | Add-on: Copilot in Word, Excel, PowerPoint, Outlook and Teams, grounded in your work data |
| Microsoft 365 Business Standard or Premium with Copilot | £18.10 or £24.60 paid yearly | Firms buying Microsoft 365 and Copilot together | Bundles the Microsoft 365 apps with Copilot; Premium adds security and device management |
| Microsoft 365 Copilot (enterprise) | £23.10 paid yearly | Larger organisations on enterprise Microsoft 365 plans | Add-on to an existing enterprise plan |
| ChatGPT Business, standard seat | £15 billed annually; £18 billed monthly | Teams of 2 to 200 people | No training on business data by default; connects to Microsoft 365, Google Workspace, Slack and more |
| ChatGPT Business, premium seat | £75 billed annually; £90 billed monthly | Heavy users inside a Business workspace | Five times the usage of a standard seat |
| ChatGPT Enterprise | On request | Larger or regulated organisations | SCIM, role-based access, compliance API, data residency options including the UK |
Two things the headline prices hide. First, the Copilot add-ons only work on top of a qualifying Microsoft 365 plan, so the real cost is the add-on plus the licence you already pay for. Microsoft also bills some advanced features by usage on top of the licence, currently including Copilot Cowork, Autopilot and the Work IQ APIs.
Second, OpenAI's UK pricing page shows pounds but doesn't say whether VAT is included, so check at checkout. Both companies change their plans often. Check the pages yourself before you sign anything.
Where Copilot is stronger
Copilot's advantage is access. With a Microsoft 365 Copilot licence it can draw on a user's email, calendar, Teams chats, meetings and SharePoint files, and it works inside the apps where that work happens. Ask it to summarise a Teams meeting you missed, draft a reply from an Outlook thread, or pull figures from last quarter's board pack into a slide, and it already knows where to look.
It also fits the IT you have. Staff sign in with their existing Microsoft accounts, and Copilot conversations are stored and governed alongside the rest of your Microsoft 365 content, with retention set in Microsoft Purview. If you already trust Microsoft with your email and files, there's no new supplier to vet.
The catch comes from the same place. Copilot shows people whatever they already have permission to see. If your SharePoint holds years of folders shared with the whole company, Copilot will surface them faster than anyone ever did by hand. Tidy up permissions before you switch it on for everyone, not after.
Where ChatGPT is stronger
ChatGPT is a general workbench. It shines at open-ended work: researching a market, rewriting a proposal, working through a spreadsheet, drafting a policy, writing a small script to clean up a data export. The Business plan includes deep research, data analysis, image generation, projects, scheduled tasks and Codex for code.
It isn't tied to one ecosystem either. ChatGPT Business connects to Google Workspace, Slack, GitHub and Microsoft 365, and has extensions for Excel, Word, PowerPoint and Google Sheets. A firm that runs on Google Workspace, or splits its work across several tools, gets more from ChatGPT than from a product built around Microsoft 365.
The trade-off is context. ChatGPT knows what you give it and what its connectors can reach. Someone has to set those connectors up and decide who may use which ones, and on the Business plan the admin controls are lighter than on Enterprise: no role-based access controls, no SCIM and no compliance API.
Data, UK GDPR and where processing happens
Neither product trains on your business content by default on its business plans. Microsoft says prompts, responses and data accessed through Microsoft Graph aren't used to train foundation models. OpenAI says it doesn't use data from ChatGPT Business, ChatGPT Enterprise or its API for training by default.
Personal accounts are a different story. OpenAI's personal plans, from Free to Pro, can be used for training unless the user opts out. If staff are using personal ChatGPT accounts for work today, fix that first, whichever tool you choose.
Location is where the two differ. ChatGPT Enterprise lets eligible customers store content at rest in the UK, one of ten regions on offer. ChatGPT Business has no data residency option. OpenAI's optional in-region GPU inference is offered in the US or Europe, not the UK, according to its business data page.
Microsoft applies its standard Microsoft 365 data-at-rest commitments to Copilot. In November 2025 it also said UK customers would get the option of having Copilot interactions processed in the UK from the end of 2025. Ask your Microsoft partner, or check your tenant, to confirm how that applies to you.
One setting to watch. Microsoft now offers Anthropic's models inside Copilot. For UK customers they're off by default, and Microsoft says they're currently excluded from its in-country processing commitments. If data location matters to you, leave that setting off until you've made a decision.
Under UK GDPR, no tool makes you compliant on its own; how you use it does. Accept the provider's data processing terms. Run a data protection impact assessment if staff will put personal data in. Write a one-page policy on what may and may not be pasted in. And if data leaves the UK, make sure the transfer has a valid safeguard, as the ICO's guidance on international transfers sets out. Our guide to using Claude with client data under UK GDPR works through the same questions for another provider, and most of the reasoning carries over.
Which one should you choose?
A small firm on Microsoft 365 that mostly wants help with email, meetings and documents: turn on Copilot Chat for everyone first, since it costs nothing extra. Then buy Microsoft 365 Copilot Business licences for the people who live in Outlook and Teams, and check they use them before buying more.
A firm on Google Workspace, or one that works across lots of different tools: ChatGPT Business. Copilot's main advantage doesn't apply to you.
A consultancy, agency or research-heavy team that writes and analyses all day: ChatGPT Business for those people, even if the firm runs on Microsoft 365. A sensible split is Copilot Chat for everyone and ChatGPT seats for the heavy users.
A regulated firm, such as a financial adviser or a law firm, that has to evidence its controls and data location: compare Microsoft 365 Copilot with ChatGPT Enterprise, not Business. Copilot keeps everything inside the Microsoft 365 controls your compliance team already knows. ChatGPT Enterprise adds UK data residency, role-based access and a compliance API. Either can work. Get each provider's processing locations and data terms in writing before any client data goes in.
Still not sure: run a four-week pilot with a handful of people on each, on real tasks. Measure the time saved and how often the output needed fixing. Your own usage data will tell you more than any comparison article, this one included.
If you want someone vendor-neutral to design that pilot, or to write the AI policy that goes with it, that's the kind of work we do as an AI consultancy for UK businesses. And if the real requirement is that client data never leaves your control, our guide to private LLMs for UK businesses covers the options beyond a chat subscription.
Sources
Checked on 24 October 2026: Microsoft Copilot for business, UK pricing, Microsoft 365 Copilot for enterprise, UK pricing, Microsoft: data, privacy and security for Copilot, Microsoft: data residency for Microsoft 365 Copilot, Microsoft: in-country data processing for Microsoft 365 Copilot (November 2025), Microsoft: Anthropic models in Microsoft Online Services, ChatGPT plans and pricing, OpenAI: ChatGPT Business overview, OpenAI: business data privacy, security and compliance, ICO guidance on international transfers. Plans and prices change, so check them before you buy. This article is general guidance, not legal advice.