When you create a Windows virtual machine on Azure at the normal pay-as-you-go price, part of what you pay every hour is the Windows Server licence. The same goes for SQL Server. If your company already bought those licences for its own servers, that means paying for them twice.

Azure Hybrid Benefit fixes this. You tell Azure you are bringing your own licence, and it stops charging you for one. For many companies moving from a server room, it is the biggest single saving on the Azure bill.

Who qualifies

The important words are Software Assurance. A licence you bought years ago without it, or whose Software Assurance has lapsed, doesn’t qualify. Check your volume licensing records before you plan around the saving.

How much it saves

Microsoft quotes savings of up to 80% on Windows Server against the standard pay-as-you-go rate, and up to 76% for Linux. Those are best cases. What you actually save depends on the region, the VM size and how much you use it. It is still large enough that we check it first on every Windows migration.

Counting the licences you need

This is where most mistakes happen. For Windows Server, Microsoft’s rules are:

• At least 8 core licences per VM. A 4-core VM still needs 8 core licences. A 12-core VM needs 12.
• One processor licence counts as 16 core licences, if your older agreement is per processor.

Standard or Datacenter makes a difference

• Windows Server Standard: each licence is used either in your server room or on Azure, not both. The one exception is a single period of up to 180 days while you migrate, so you can run old and new side by side and test.
• Windows Server Datacenter: for Azure VMs, Microsoft allows the same licences to be used in your server room and on Azure at the same time, with no time limit.

If you are staying hybrid for a long time, with some servers on site and some on Azure, Datacenter licences can be worth their higher price. SQL Server also gets 180 days of overlap during a migration.

Old Windows and SQL versions

Many server rooms still run Windows Server 2012 or 2012 R2. Microsoft has been giving these servers free security updates on Azure, but the last of those updates ends on 13 October 2026. After that there are no more security updates for Windows Server 2012 anywhere, on Azure or off it.

If you still run 2012, treat the migration as the moment to upgrade the operating system, not just to move it. Older SQL Server versions in their extended support period can also get security updates on Azure VMs at no extra charge, as long as the SQL IaaS Agent extension is running. Check the dates for your version before you rely on it.

A licence check in five steps

1. List your servers: every Windows Server and SQL Server you plan to move, with its edition and version.
2. Find the paperwork: your volume licensing agreement, how many core (or processor) licences you own, and which have active Software Assurance.
3. Size the Azure VMs: most servers can move to a smaller VM than the hardware they run on today, which also lowers the licences they need.
4. Match licences to VMs, starting with the largest and longest-running, where the benefit saves most.
5. Price both ways: with the benefit and without it, so you know what the licences are worth before you decide to renew Software Assurance.

How to switch it on

1. New Windows VMs: tick the box under Licensing when you create the VM, confirming you have eligible licences.
2. Existing Windows VMs: change the licensing setting in the VM’s configuration. You don’t need to rebuild it.
3. Azure SQL Database and Managed Instance: choose the option to use your existing SQL Server licence in the compute settings.
4. Check the bill. VMs using the benefit show as “WindowsServerBYOL” in the usage details, and Azure can list every VM that has it on.

Keep records

Turning the benefit on is a promise that you own the licences. Microsoft reserves the right to audit at any time. Keep a simple sheet with your licence numbers, Software Assurance end dates and which VMs use which licences, and update it whenever you add or remove a VM.

Mistakes we see

• Ticking the box without Software Assurance. It works technically, which is why it gets missed until an audit.
• Letting Software Assurance lapse. When it ends, so does your right to the benefit. Put the renewal date in a calendar.
• Running Standard licences in both places after the 180 days are up.
• Counting small VMs at their real size. A 2-core VM still uses 8 core licences.
• Forgetting reservations. The benefit covers the licence; an Azure reservation or savings plan cuts the compute price too. Used together, they make the biggest difference.

Where DevOps TechLab fits

DevOps TechLab is a Microsoft Solutions Partner for Cloud and AI Platforms and for Infrastructure (Azure). Every free migration assessment we run includes a licence check: what you own, what still has Software Assurance, how many cores each VM needs, and what that means for your monthly Azure bill in rupees.