A global Microsoft outage that spread across 74 countries left British businesses fighting to access Outlook, Teams and other Microsoft 365 services on Friday — and analysts warn the bill could run into the billions.

The disruption began on Thursday evening and quickly cascaded through UK commerce. Supermarket giant Asda reported failures in online customer registrations, password resets and email changes, though City AM understands its systems have since been restored.

Riz Malik, an independent financial adviser at R3 Wealth, did not mince words: "Friday the 13th spells doom for Microsoft and many of those that rely on their services. This is a bad day for UK plc productivity."

Who was hit, and how hard?

The fallout crossed several sectors at once:

• Asda — online registrations, password resets and email changes broke; operations are now understood to be restored.
• NatWest — the lender was caught up in the communication failures sweeping the City.
• Great Western Railway — emailed ticket confirmations were unavailable, and the operator told passengers to use its app or website instead.

The pain wasn't evenly spread. Smaller businesses that lean on Microsoft's software to talk to customers, suppliers and lenders face the sharpest financial risk, particularly where money moves against a clock.

Why the losses could mount

Samuel Mather-Holgate, managing director of Mather and Murray Financial, warned the disruption could become one of the "most economically damaging technology failures in history" and cost businesses billions.

Property transactions show the mechanism. When solicitors, lenders and brokers can't exchange documents, completions stall. That's cash and contracts sitting idle — not just inconvenience.

Regulators add another layer of pressure. Financial services firms must demonstrate they can withstand major technology disruptions, so an outage like this isn't merely operational. It's a compliance exposure too.

Rob Mason, director of regulatory intelligence at Global Relay, said firms could not afford to "go dark", and that the outage would prompt fresh questions about operational resilience and dependence on third-party providers.

How concentrated is the UK's cloud market?

Very. Microsoft and Amazon Web Services together control an estimated 70 to 80 per cent of the UK's public cloud market (rented, off-site computing infrastructure). That concentration is precisely why one failure bit so widely.

Mark Boost, chief executive of UK cloud provider Civo, put it plainly: "When the same company runs the cloud, email, documents and collaboration tools, a single failure takes everything down together."

His point is structural, not rhetorical. Bundling infrastructure, communications and productivity software under one roof means there is no partial outage. Functions fail in unison.

Does Microsoft actually lose from this?

Probably not much. Amish Patel, head of equity research at Raymond James, said the direct financial impact on Microsoft was likely to be negligible, given the company's scale and the difficulty customers face in switching providers.

The lock-in cuts both ways. Microsoft's entrenched position means businesses are unlikely to abandon its services overnight, however painful Friday proved. Patel framed the real question differently: "The more interesting question is whether repeated outages begin to change how businesses think about their dependence on a single technology provider."

That's a boardroom issue now. Every CIO watching Teams go dark on a Friday has a fresh argument for contingency planning, multi-vendor sourcing, or at least a documented fallback.

What happens next?

Microsoft said on Friday it was making "additional progress toward service recovery", with traffic gradually returning after the disruption spread across 74 countries. The company attributed the problems to servers becoming unexpectedly unavailable and said there was no evidence of a cyberattack.

So no attack, and recovery under way. But the underlying arithmetic hasn't changed: when two vendors control up to 80 per cent of a market that an entire economy runs on, resilience isn't a procurement detail. It's a national economic exposure — and Friday the 13th just priced it.