Windows 10 End of Support: What London and UK SMEs Must Do Before 13 October

A guide for London and UK businesses with 10 to 100 staff: what changes on 13 October 2026, what each option really costs per device, and the questions your IT support company should already have answered.

By Sanish Satheesan CISSP, CIO at Astec IT · August 2026

Windows 10 end of support is not a date in the future. Microsoft stopped supporting Windows 10 on 14 October 2025. What lands on 13 October 2026 is the end of the first year of paid Extended Security Updates — the point where the cost of staying put doubles. This guide is written for owners, MDs and finance leads at London and UK businesses between 10 and 100 staff: what actually changes, what each route costs, what it does to your Cyber Essentials certification, and what to put to your managed IT support company this month.

What is happening to Windows 10 in October 2026?

ESU is also narrower than most people assume: critical and important security updates only, with no feature updates, no non-security fixes and no general technical support. Eligibility is narrow too — Enterprise, Education and Pro in commercial use, on version 22H2. Windows 10 Home is not eligible, which catches out plenty of businesses where a few people bought their own laptops.

Source: StatCounter Global Stats, desktop Windows version market share, United Kingdom, July 2026.

What happens if you do nothing?

The commercial consequences arrive sooner than the technical ones. For a London SME, client security questionnaires ask which operating systems you run, insurers ask at renewal, and a certification you may already hold has a firm view on it.

How much do Windows 10 Extended Security Updates cost?

Run that against a replacement laptop and the arithmetic gets uncomfortable. Three years of ESU costs a meaningful fraction of a new machine that would arrive with Windows 11, a fresh warranty and hardware that isn’t already five years old. You are paying an escalating fee to keep something alive rather than putting the same money toward replacing it.

One exception is worth knowing. Windows 10 virtual machines in Windows 365 or Azure Virtual Desktop get ESU at no additional cost, and physical endpoints connecting to a Windows 365 Cloud PC are covered too. If you already run Microsoft 365 and cloud management at any scale, that changes the sums.

Does Windows 10 affect your Cyber Essentials certification?

• Patching within 14 days. All high-risk or critical security updates must be applied within 14 days, for operating systems and firmware as well as applications. Miss it and the assessment fails outright.
• MFA on all cloud services. Multi-factor authentication is mandatory wherever a cloud service offers it, whether it is free or chargeable. Another automatic fail.
• Scope has to be explicit. You now describe your scope in detail, name the legal entities covered, and state what is excluded — so a cupboard of old Windows 10 machines is harder to leave unmentioned.

If your certification renews in the next twelve months, the device list and the patching evidence are the two things to have straight. That is ordinary work for whoever provides your Cyber Essentials certification support — but only if somebody is actually tracking it.

Is Microsoft 365 still supported on Windows 10?

Your four options, compared

The fourth option is the one most London SMEs haven’t priced. Windows 365 Cloud PCs and virtual desktops include ESU for the Windows 10 endpoints connecting to them, and they take the hardware refresh cycle off your books. Not right for everyone — heavy design or data work still wants a real machine — but worth a look before you sign off a capital spend.

What if your PCs can’t run Windows 11?

A seven-week plan for the 13 October deadline

1. Get the device list. Every machine, its Windows version, edition, age and whether it passes the Windows 11 requirements. A day’s work, not a project.

2. Split it three ways. Upgrade in place, firmware fix then upgrade, replace. The middle group is usually larger than anyone expects.

3. Test your critical applications. Take the two or three systems the business cannot work without and confirm them on Windows 11 before you touch anyone’s laptop.

4. Order hardware now. Lead times are the one variable you don’t control. Anything being replaced should be on order this month.

5. Decide the ESU question deliberately. If a handful of machines can’t move by 13 October, enrol those specific devices — and write down the date you will stop paying.

6. Roll out in batches. A department at a time, with a rollback plan. Check your backups and disaster recovery work before the first batch, not after.

7. Update your evidence. Refresh the asset inventory and patching records so the next Cyber Essentials assessment or insurance renewal is form-filling rather than an investigation.

Questions to ask your IT support company this week

• How many of our devices are still on Windows 10, and which people have them? A specific number and a list. Not “a few”.
  
• Which of those can upgrade to Windows 11 today, and which cannot, and why? The “why” should name the blocker — firmware setting, processor, or an application.
• Are any of them enrolled in ESU, and what did it cost us? If they enrolled devices without telling you, that is worth knowing. If they didn’t, ask what has protected those machines since October 2025.
• What is the plan and the cost to get everything onto a supported operating system? With dates.
• When did you first raise this with us, and how? An honest answer tells you most of what you need to know about the relationship.
• What else is unsupported or approaching end of life? Servers, firewalls, backup appliances, applications.

The point isn’t to catch anyone out. It is that proactive IT support means hearing about this in 2025 with a costed plan attached, not in 2026 from a blog. We run against a documented device inventory with proactive device monitoring, and end-of-life dates are part of the biannual technology review rather than a surprise. If your IT company can’t produce the list, that gap is the finding.

IT support for London and UK SMEs

Areas we cover: London · Greater London · Hertfordshire · Kent · Surrey · Leicester · Liverpool · Manchester

Frequently asked questions about Windows 10 end of support

You have around seven weeks. Enough — if week one produces a device list rather than a meeting.

Start with one question, in writing: how many of our machines are still on Windows 10, which can move to Windows 11, and what is the plan for the ones that can’t? Whoever manages your technology should answer from records they already hold. If it takes weeks, or arrives as a proposal for a chargeable audit, that tells you something separate from the Windows question. For related ground on security and switching, our resource library for UK SMEs covers it.

Sanish Satheesan CISSP is Chief Information Officer at Astec IT. He has worked in IT for more than 15 years, including 11 years at Netstar, where he rose from service engineer to professional services manager, and two and a half years as Information Security Manager at CRU. Since 2021 he has held the ISC2 Certified Information Systems Security Professional (CISSP) certification, and he studied at Kingston University. He writes regularly about cyber resilience, incident response and IT audits for UK SMEs.

Connect with Sanish on LinkedIn

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2. Shadow AI: the tools your staff use that your IT partner can’t see
3. Cyber security fundamentals and staff security training for UK SME
4. About Astec IT and how we work