Slack vs Microsoft Teams: which is better for your business?

Slack and Microsoft Teams do the same basic job: they give your team one place to message each other instead of email. But they come from very different places, and the right choice depends less on features than on what your business already uses.

The short answer: if your business is on Microsoft 365, use Teams. If it isn’t, and your team lives in lots of different web apps, Slack is worth a serious look.

At a glance

	Microsoft Teams	Slack
Best for	Businesses on Microsoft 365	Teams that work across lots of different apps
Cost	Included in most Microsoft 365 business plans	Free plan; paid plans from £5.75 per user per month (annual billing)
Meetings	Strong: large video meetings, recording, transcripts	Huddles for quick calls; most firms add Zoom or Teams for bigger meetings
Phone calls	Can replace your phone system (Teams Phone)	No business phone system
Files	Stored in SharePoint and OneDrive	Stored in Slack, or linked from Google Drive, Box and others
AI	Copilot (Copilot Chat included; full Copilot is a paid add-on)	Basic AI on every plan; advanced AI on Business+
Free plan	Free for personal use	Free, but only 90 days of message history

Slack prices from Slack’s UK pricing page, checked 10 November 2026.

Cost: Teams is usually already paid for

This is where most small businesses decide. Teams is included in most Microsoft 365 business plans, so if you already pay for Outlook, Word and Excel, you probably already have it. Microsoft now also sells some Microsoft 365 plans without Teams, so check what is on your invoice.

Slack has a genuinely useful free plan, but it only shows your last 90 days of messages and files, and calls are one-to-one only. For a business, the paid plans are where Slack becomes usable: Pro is £5.75 per user per month on annual billing, and Business+ is £12, which adds Slack’s advanced AI and more admin and security controls.

For a 20-person firm already on Microsoft 365, adding Slack Pro costs roughly £1,400 a year on top of what you pay Microsoft, before you add a separate meetings tool.

Chat: Slack still feels nicer

Day to day, Slack is the more pleasant place to chat. Threads, search, reminders and its huge app directory make it popular with teams that use lots of different software. If your business runs on tools like Google Workspace, HubSpot, Jira or Xero and you want them all feeding one chat window, Slack does that very well.

Teams has caught up a lot. Threads, channels, reactions and rich formatting are all there, and because it sits inside Microsoft 365, sharing a file shares the real SharePoint or OneDrive file, one version with proper permissions, rather than a copy.

Meetings and phone calls: Teams wins clearly

Teams is built around meetings. Large video calls, recordings, live captions, transcripts and meeting notes are all part of it, and it works directly with Outlook calendars.

It can also become your phone system. Teams Phone (what used to be called Microsoft 365 Business Voice) lets staff make and take ordinary phone calls from Teams on a laptop or mobile. With the UK’s old phone network being switched off, that matters: see the 2027 phone switch-off and our telecoms service.

Slack’s Huddles do a quick chat well, but plenty of Slack businesses end up paying for Zoom or Teams as well for client meetings. That means more accounts and more places for things to go wrong.

AI: both have it now

This is the biggest change since we first wrote this article.

• Teams works with Microsoft 365 Copilot. Copilot Chat is included for business users; the full Copilot, which summarises meetings you missed and drafts replies from your emails and files, is a paid add-on.
• Slack now includes basic AI on every plan, such as conversation summaries and AI search. Its more advanced AI features sit on the Business+ plan.

Either way, AI is only as safe as the permissions behind it. If staff can open files they were never meant to see, AI will happily summarise them too. Tidy up who has access to what before you switch AI on.

Security: what has changed

When we first wrote this in 2021, the security question was mostly about passwords. Today the bigger risk is people pretending to be someone they’re not.

Attackers now message staff directly in Teams and Slack, posing as the IT helpdesk or a senior manager, and ask them to approve a login or pay an invoice. A chat message feels more trustworthy than an email, which is exactly why it works.

Whichever app you choose:

• Restrict external messaging to the organisations you actually work with, rather than leaving it open to anyone.
• Turn on multi-factor authentication for every account, and sign in with your Microsoft 365 or Google account rather than a separate password.
• Tell staff how IT will contact them, and that a genuine IT team will never ask for a password or an MFA code in a chat.
• Back it up. Microsoft and Slack keep the service running, but that is not the same as a backup you can restore from. See why your business needs to back up Microsoft 365.

Which one to choose

Choose Teams if you already use Microsoft 365 or hold a lot of meetings. It can replace your phone system at the same time.

Choose Slack if you aren’t a Microsoft business and your team works across many different web apps. Budget for a meetings tool on top.

Avoid running both. It’s common, and it usually means conversations split across two places, two sets of security settings and two bills.

How Jera can help

We set up and look after Microsoft 365 and Teams for businesses across Edinburgh, Glasgow and Aberdeenshire, from moving off Slack to setting up Teams Phone and locking down external access. If you’re weighing up the switch, book a call and we’ll tell you honestly which suits your business.