The short answer
A UK professional services firm should use the assistant already included in its Microsoft 365 or Google Workspace subscription, then buy paid seats only for the people whose work needs the assistant to read the firm's own files. Microsoft draws that line in its own documentation: the included chat searches the internet, the licensed one searches what the work account can reach. Everything else is priced against that gap.
Key takeaways
- Two of the subscriptions a firm already renews now carry a general assistant. Google folded Gemini into its Workspace business plans and raised the plan price instead of selling an add-on.
- The paid seat buys reach into your own content. Microsoft separates included web-based chat from licensed work-based chat, and that is the distinction worth paying for.
- Seats are priced per person and the saving accrues only to the people who do the task, so licensing the whole firm pays for everyone to clear a bar most of them will not.
- Twelve months of one seat divided by an internal hourly cost gives the minutes per week that seat has to save. Test it against one desk before signing for twenty.
- A subscription and a lump sum licence are not treated alike for tax, so the five year comparison a supplier shows you is not the comparison your accounts will make.
The question usually arrives already narrowed. A managing partner forwards a comparison of a dozen products, asks which of them the practice should be on, and the assumption sitting underneath is that the firm currently has nothing. Every result on the first page of that search is a ranked list of tools, and every one of those lists is published by a company that sells implementation.
Most UK firms of this size already pay for a general assistant and have not switched it on. That changes the question from which product to buy into a narrower and much cheaper one: what does the capability in the demonstration do that the licence on the invoice already does, and is the difference worth a second subscription for every head in the building.
Start with the subscription you already renew
In January 2025 Google stopped selling artificial intelligence as an add-on to Workspace and put it in the plan. Its own announcement gives the arithmetic: a Business Standard customer who had bought the Gemini Business add-on previously paid $32 per user, per month, and now pays $14, which is $2 more than the plan cost without it. Microsoft made a comparable move on the chat tier rather than on the price.
Google Workspace Business Standard
£11.80 per user per month
Already included
The Gemini assistant in Gmail and Docs, on the published price list, with no separate artificial intelligence line on the bill.
Not included
Anything that depends on a system outside Workspace, such as your practice management or time recording software.
Microsoft 365 Business Standard
Copilot Chat at no extra cost
Already included
Web-based Copilot Chat, which Microsoft documents as automatically included with an eligible subscription and which shows results from the internet.
Not included
Work-based chat, which shows results the work account can access. That needs the paid Copilot licence.
A paid assistant seat, either vendor
The upgrade under discussion
What you are buying
Reach into the firm's own documents and mail, and the assistant inside the applications rather than beside them.
What you are not buying
A tool that knows your engagement letters or your file naming without somebody putting them somewhere it can read.
The paid seat buys access to your own files
Microsoft's licensing documentation separates the two tiers in a single sentence, and no sales deck leads with it. Web-based chat shows results from the internet and is automatically included at no extra cost with an eligible subscription. Work-based chat shows results that the work or school account can access, and is available with a Copilot licence.
For a practice that distinction is close to the whole value. Summarising a public tax change is useful and free. Summarising the file note on a specific client, drafting from the engagement letter you actually sent, or finding the last four times the firm answered a question like this one, all require the assistant to read the firm's own material. That is the capability under discussion, and it is also the capability that raises the questions about what the software may do with the content it reads, which is the same test as any other automated task: what the rule at the end of the work will accept.
Price the seat against the person in it
A per-seat price and a per-task saving do not meet at the level of the firm. The licence is charged for everybody. The hours come back to the two or six people who do the work the assistant shortens. Quoting a firm-wide annual figure against a firm-wide hours estimate hides that, and it is how a sensible tool ends up looking expensive and a poor one ends up looking cheap.
Run it the other way. The arithmetic below is illustrative and uses placeholder figures, so put your own seat price and your own internal hourly cost into it.
One seat, at an illustrative £22 per user per month
£264 a year
Divided by an internal cost of £45 an hour, which you should replace with your own
5.9 hours a year
Spread across a working year, the time that seat has to save its holder
About 7 minutes a week
Now count only the people whose weekly work it genuinely shortens, rather than the headcount
That is your licence count
Before the renewal date
Not sure whether you are about to buy something twice?
Free to your firm. The agency pays us, and only if the relationship works, which is why we would rather tell you the licence you already hold covers it than introduce somebody to sell you another one.
Get a recommendationThe subscription and the one-off build are not taxed alike
HMRC's Business Income Manual says that unless periodical payments are instalments of a capital sum, such payments are deductible. The same guidance tells inspectors not to contend that software with an expected useful life of less than two years is capital, and treats a lump sum paid for a licence as analogous to a premium on a lease, which is capital.
Your own tax people will know this better than we do. The reason it belongs in a buying decision is that the five year total a supplier puts next to a commissioned build is not the comparison your accounts will make, and that gap is one of the reasons licensing and building cross over where they do.
When a firm should not buy an AI seat yet
Two conditions make the purchase premature, and neither is about the software.
- The assistant already inside the subscription has not been switched on and used for a month. Until it has, nobody in the firm can say what the paid tier would add, and the demonstration is the only evidence in the room
- Nobody has measured the hours the tool is supposed to recover. A UK firm buying on a figure from a vendor's case study is buying against somebody else's desk, and the fix is to measure the task before anyone quotes for it
Saying so costs us the introduction fee, because we are paid by the agency and only when a relationship works. Where a supplier genuinely is needed, what we assess before recommending anyone is set out for professional services firms across the country.
Frequently asked questions
What partners ask before approving the licence.
Do you have to pay extra for AI in Microsoft 365 or Google Workspace?
Not for the general assistant. Microsoft says web-based Copilot Chat is automatically included at no extra cost with an eligible Microsoft 365 subscription, including Business Standard and Business Premium. Google includes Gemini in its Workspace business plans and raised the plan price rather than selling it as an add-on.
What does a paid Microsoft 365 Copilot licence actually add?
Reach into your own content. Microsoft's licensing documentation separates web-based chat, which shows results from the internet and is included, from work-based chat, which shows results the work account can access and requires a Copilot licence. For a practice, the second one is where the billable hours sit.
How many AI seats should a firm of 20 people buy?
As many as there are people whose weekly work the assistant actually shortens, which is rarely everyone. Divide twelve months of one seat by the internal hourly cost of the person sitting in it. That gives the minutes per week that seat has to save, and it is a number a partner can test against a real desk before signing for the firm.
Is an AI subscription a deductible expense for a UK firm?
Periodical payments are usually deductible. HMRC's Business Income Manual states that unless periodical payments can be shown to be instalments of a capital sum, such payments are deductible, and that software with an expected useful life of under two years should not be treated as capital. A lump sum paid for a licence is treated differently. Ask your own tax people before assuming the two options compare on the headline figure.
When should a firm not buy AI tools yet?
When nobody has measured the hours the tool is supposed to recover, and when the assistant already inside the subscription has not been switched on and used for a month. Both cost nothing to fix and both change the answer. A UK firm that buys before either is comparing a demonstration against a guess.
Sources and useful reading
- Google Workspace, the future of AI-powered work for every business, 15 January 2025, for the add-on price it replaced and the new plan price.
- Google Workspace published pricing, for the Business Standard rate and what each plan lists as included.
- Microsoft, license options for Microsoft Copilot, for web-based chat against work-based chat and the eligible subscriptions.
- HMRC Business Income Manual BIM35810, on periodical payments and the two year test for computer software.
This article is commercial decision support and is not tax advice. Vendor prices are the published figures at the date above. They exclude VAT and they change. The seat arithmetic is illustrative and uses placeholder figures rather than quoted ones.