Internal chat tool rationalization addresses one of the most common forms of quiet overspend in the collaboration stack: paying for two messaging platforms that do substantially the same job. The usual pattern is Slack adopted early by teams who liked it, then Microsoft Teams arriving later bundled into Microsoft 365 licences the company already pays for. Both run in parallel, both carry cost and administrative overhead, and nobody owns the decision to choose one.
This is a stack decision, not a single vendor decision, which is why it connects up into the bundled digital workplace cost optimization view. The saving rarely lives in one tool. It lives in removing the duplication between them while protecting the work that depends on each.
Why organizations end up paying for two chat tools
Duplication is rarely a decision. It is an accumulation. A few teams adopt Slack for its integrations and culture. The company then standardizes on Microsoft 365 for productivity and security, and Teams comes bundled at no extra line item. Now both exist. Because Teams feels free and Slack feels embedded, neither gets challenged, and the organization pays for Slack on top of a Teams entitlement it has already bought.
The cost is not only the Slack subscription. It is the split administration, the duplicated integrations, the security and compliance surface across two platforms, and the friction of staff not knowing where a conversation lives. Internal chat tool rationalization puts a number on that and forces the choice.
How to run an internal chat tool rationalization
Map what you actually pay for and use
Start with the entitlements. If you license Microsoft 365 at a tier that includes Teams, you already own a chat platform. Then measure real usage of each tool: active users, message volume, the integrations in genuine use, and the teams with a dependency that would be costly to break. You cannot rationalize what you have not measured.
Decide the standard, with eyes open
In most cases the tool already bundled into Microsoft 365 becomes the default, because you pay for it regardless. That does not make Slack worthless. Some teams rely on specific Slack integrations or external workflows that Teams does not replicate cleanly. The decision is which platform is the standard for the organization, and where a justified exception remains.
Protect the dependencies before you cut
The fastest way to turn a saving into a disruption is to remove a tool a team genuinely depends on. Identify those teams first, understand what they rely on, and plan the migration or the exception before you touch the subscription. A smaller, justified Slack footprint that protects real dependencies is often the right answer, not a hard cut to zero.
The cost of getting chat tool overlap wrong
Cut too hard and you break workflows, push teams toward shadow tools, and create more sprawl than you removed. Cut too slow and you keep paying for duplication indefinitely while the Slack renewal climbs each year. The discipline is to move deliberately: decide the standard, protect the exceptions, migrate the rest, and time any Slack reduction to the renewal so you keep your leverage, as covered in negotiating Slack enterprise renewals.
Sequencing the rationalization
Take it in order. Confirm the Teams entitlement you already own. Measure usage and identify dependencies. Decide the standard and the exceptions. Communicate the change and migrate the channels and integrations that move. Then right size or retire the Slack subscription at the renewal, keeping a justified footprint where the dependency is real. Each step reduces risk while the saving accrues, and the price discipline that makes the final cut land is the same one in Slack pricing and how to reduce it.
Where chat rationalization fits the wider stack review
Chat is one overlap in a collaboration stack that usually duplicates across messaging, meetings, and video too. Resolving the chat overlap in isolation captures part of the saving, but the full picture comes from reviewing the whole stack together. This is the work in our collaboration tool rationalization service, which decides the standard for each capability, removes the duplication, and feeds the result into the bundled engagement across the entire digital workplace spend.
Source: Microsoft 365 and Slack plan documentation, microsoft.com and slack.com, as of June 2026. Bundled entitlements and plan contents change often, so confirm what your licences include against your own agreements.