The Microsoft On-Prem-to-365
Migration Deadline Tracker
Every end-of-support and retirement date between 2025 and 2027, in one place. All dates verified against Microsoft Lifecycle.
Most of the deadlines you're worried about have already passed.
That's the honest summary of the 2025-to-2027 window. Exchange Server 2016 and 2019, Skype for Business Server, Office 2016 and 2019, and Windows 10 all lost support in October 2025. SharePoint Server 2016 and 2019, SQL Server 2016, and Project Server followed in July 2026. If you're running any of those today, you're not planning for a deadline — you're already past one.
Below is every date that matters between now and the end of 2027, what's lapsed, what's still ahead, and the three traps that catch teams who read the calendar and stop there.
A note on freshness: Microsoft moves cloud-side dates with little notice, so we re-check those monthly and re-check the full table quarterly. If you're reading this more than a few months after the verification date above, treat the on-prem dates as solid and double-check anything cloud-side.
ON THIS PAGE
The deadline tracker
Ordered by date. Lapsed dates are behind you — no security updates, no other updates, and no assisted support, free or paid.
Exchange Server 2016 and 2019. Skype for Business Server 2015 and 2019. Office 2016 and 2019, including Outlook, Word, Excel, Visio and Project. Windows 10, every edition.
Windows 10 is the one exception worth naming. A paid Extended Security Updates program exists — commercial customers can buy up to three years of patches counting from October 2025. It's a bridge, not a fix, and the cost rises each year you stay on it. Nothing else on this list has an equivalent program.
SharePoint Add-ins and the older SharePoint workflows retire — in Microsoft 365 only. On-prem farms are not affected.
SharePoint Server 2016 and 2019. SQL Server 2016. Project Server 2016 and 2019. InfoPath 2013. SharePoint Designer 2013.
Exchange Online starts switching off Exchange Web Services — the older programming interface that many integrations and migration tools still rely on.
Office LTSC 2021 and the 2021 versions of Word, Excel, Outlook, Visio and Project. Also the third and final year of paid updates for Windows Server 2012 and 2012 R2.
.NET 8, the long-term support release that a great many line-of-business applications run on.
Office Online Server retires — the component that provides browser-based document editing inside an on-prem SharePoint farm.
System Center 2016 and BizTalk Server 2016. One day earlier than the Windows Server 2016 date below — see the traps section.
Windows Server 2016, along with Hyper-V Server 2016 and the web server role that runs on it.
Exchange Web Services is removed permanently, with no option to switch it back on. Anything still built on it has to move to Microsoft Graph.
SQL Server 2017.
Three traps in this calendar
Reading the dates is the easy part. These are where teams get caught out.
Dates that look like the same date
January 11 and January 12, 2027 are two separate deadlines. System Center 2016 and BizTalk Server 2016 go on the 11th; Windows Server 2016 goes on the 12th. October 13 and October 14 have caused the same confusion two years running. Plan against the exact date, not the month — a change window booked for the wrong side of a weekend is a cheap mistake that gets expensive at audit.
The cloud deadline arrives before the on-prem one
Exchange Web Services is the clearest example. It affects Exchange Online only — Exchange Server on-prem is untouched. But if you're mid-migration, your migration tooling very likely depends on it. From October 1, 2026, any tenant that's taken no action has the setting flipped off. Admins can re-enable it and approve specific applications, but only until April 2027 — after that there's no re-enabling it. Scope your project from the earliest forcing event, not the headline on-prem date.
Subscription Edition has a horizon too
Subscription Edition products are the supported on-prem path now, and they have no fixed end-of-support date — but that isn't the same thing as forever. Support continues only while you stay current with updates, so the countdown becomes an ongoing obligation. Microsoft also publishes an earliest-possible end-of-support date for each product, and they aren't all the same: Exchange, SharePoint and Skype for Business Subscription Editions won't end before December 31, 2035. Project Server Subscription Edition won't end before December 31, 2031 — a full four years earlier. If your plan treats all four as one platform with one horizon, that gap will find you.
Know exactly what's lapsed and what's coming for your estate
Skip the guesswork — we'll map everything you're running against these dates for you.
What moves, and what has to be rebuilt
Meeting the deadline is the easy part. The expensive part is what doesn't come with you.
Moves cleanly, in most tenants
- Mailboxes, calendars and contacts into Exchange Online
- Documents, libraries and most site content into SharePoint Online
- Content types, metadata and term stores
- User accounts synchronized into Microsoft Entra
- Most public folder data, moved in stages
- Standard reporting through the Power BI service
- Files from the retired Stream service
Must be rebuilt
- Mail rules that depend on software installed on your own mail servers
- InfoPath forms — no conversion tool exists, and none is coming
- Older SharePoint workflows, rebuilt in Power Automate
- Custom code on a SharePoint farm, rebuilt on the modern framework
- Skype for Business voice and telephony, redesigned in Microsoft Teams
- Reports bound to a data source that stays on-prem
- Approval history and workflow run records, which usually don't travel at all
The right column is where projects overrun. None of it is a file copy — each row is a small build with its own testing and sign-off, and the work usually surfaces late because nobody wrote down that the form or the workflow existed.
What to do with this
Find out what you're actually running. Not what the architecture diagram says. Forms, workflows and custom code are almost never documented, and they're the items that set your timeline.
Sort by the earliest forcing event, not the product. One cloud-side date can pull a whole project forward by a year.
Cost the rebuild column separately. Treating it as part of the migration is the single most common reason these projects run over.
Decide on Subscription Edition deliberately. It's a legitimate answer for estates carrying heavy custom code. It's a poor answer if you chose it only to avoid a decision.
The organizations that moved early moved the easy things. What's left across most estates is the awkward residue: the form nobody documented, the workflow one person understood, the integration written by someone who left in 2019. That's the work, and a date on a calendar tells you nothing about how much of it you have.
WME runs assessments that inventory exactly this before anyone commits to a plan.
What the assessment covers
A full inventory of forms, workflows and custom code — not just what the architecture diagram shows
Your earliest forcing event, mapped against this tracker
A rebuild cost estimated separately from the migration itself
No pricing quoted until we know what you're carrying.
