Microsoft Teams or Slack: what each costs, what the free plans keep, and how each works with outsiders

As each vendor published them in October 2026. Microsoft's Irish pages give euro, per user per month, on an annual subscription paid yearly, before VAT. Slack's Irish pricing page showed its prices in US dollars when we read it, and did not say whether tax is added. Slack's help centre says it sets a workspace's billing currency from its location when the workspace is created, and lists the euro among the five currencies it bills in; we could not read a euro price.

Slack's free plan keeps the most recent 90 days of messages and files visible, and data in the workspace more than a year old is deleted. It allows up to ten apps, huddles between two people only, and Slack Connect for one-to-one messages with people at other organisations, not shared channels. Guest accounts are for paid plans only.

Microsoft's free Teams is Teams for home. Its Irish page says small businesses can use it, and gives group calls and meetings of up to 60 minutes with up to 100 participants, one-to-one calls of up to 30 hours between Teams users, and 5 GB of cloud storage per user. For business features it points to a business plan.

Slack works with other organisations through Slack Connect. A Slack Connect channel can take up to 250 organisations, each of which must be on a paid Slack plan, and the organisation that owns the channel decides who is invited. A direct message with someone outside can be started on any plan.

Slack suggests guest accounts for people who don't have Slack at their own company, such as a contractor, and Slack Connect for people who do. Guests are on paid plans only: multi-channel guests are billed as regular members, and single-channel guests are free, up to five for each paid active member.

Teams has two routes. External access lets your staff find, call, chat and set up meetings with people at other organisations who use Teams; Microsoft has it on by default, and it doesn't share files. Guest access adds a person from outside to a team, with a guest account in your directory, so they can chat, meet and work on the team's files. Microsoft says anyone with a business or consumer email address, such as Outlook or Gmail, can be a guest, and that no extra Microsoft 365 licence is needed; its Irish comparison lists guest access on Business Basic and Standard.

A team's files are kept in its SharePoint site, and Microsoft says guest access in Teams needs settings in Microsoft Entra ID, Microsoft 365 Groups and SharePoint as well; SharePoint for a small business covers the SharePoint side. Teams also has shared channels, which let people from outside into one channel without a guest account, for people who sign in with a Microsoft Entra work or school account.

On 12 September 2025 the European Commission accepted commitments from Microsoft over the tying of Teams to Word, Excel, PowerPoint and Outlook in its Office 365 and Microsoft 365 business suites, and made them legally binding. Under them, Microsoft makes versions of those suites available without Teams, at a reduced price, to customers buying in the EEA, lets customers on long-term licences switch to them, gives tools that compete with Teams interoperability with certain Microsoft products, and lets customers move their data out of Teams.

The Commission says the commitments stay in force for seven years, and those on interoperability and data portability for ten. It opened the case on 27 July 2023, after a complaint by Slack Technologies.

Microsoft's Irish plans page in October 2026 listed the EEA versions by name, such as Microsoft 365 Business Standard with Copilot EEA (no Teams), with business email and the Office apps included. Google Workspace or Microsoft 365 compares those plans for email and files.

From what each vendor's own pages include: