Ask three suppliers which plan your business should be on and you will get three confident, contradictory answers. All of them will be defensible. None of them will be based on your actual risk.
Choosing a Microsoft 365 licence is not a productivity decision. It is a security, compliance and budget decision wearing a productivity badge, and the gap between the cheapest and dearest option runs to tens of thousands of pounds over a typical contract. The three plans most businesses end up comparing — Business Premium, E3 and E5 — are not simply small, medium and large versions of the same thing.
This guide breaks down what each tier genuinely includes, where each one quietly leaves a gap, and how to match the decision to the size and obligations of your business. It assumes you already have a tenant. If you are worried about what happens to the data inside it, read our companion piece on Microsoft 365 backup first, because no licence tier covers that — a distinction most managed IT services proposals gloss over entirely.
Table of contents
- Why the Microsoft 365 Licence Question Is Harder Than It Looks
- What Microsoft 365 Business Premium Actually Includes
- What E3 Adds Above Business Premium
- What E3 Quietly Takes Away
- What E5 Adds on Top of E3
- The 300-Seat Cap and When Your Microsoft 365 Licence Must Change
- What No Microsoft 365 Licence Gives You
- The Real Cost of Each Microsoft 365 Licence Over Three Years
- Mixing Licences Instead of Buying One Tier for Everyone
- How to Choose Your Microsoft 365 Licence: A Decision Framework
- Buying Terms That Change What Your Microsoft 365 Licence Really Costs
- Frequently Asked Questions About Your Microsoft 365 Licence
- Getting the Decision Right
Why the Microsoft 365 Licence Question Is Harder Than It Looks
The comparison tables published by resellers are accurate and almost useless. They list features rather than outcomes, and they hide the one fact that decides most cases.
The three plans are not a straight ladder
Business Premium sits in the Business family. E3 and E5 sit in the Enterprise family. They were designed for different customers, priced on different logic, and they do not stack neatly on top of one another. Moving from Business Premium to E3 gains you several capabilities and loses you others outright. Anyone describing your Microsoft 365 licence options as small, medium and large has not read the fine print.
Feature lists compare badly against each other
Microsoft names products by capability tier — Plan 1, Plan 2, P1, P2 — and the same word means different things in different families. Defender for Business is not Defender for Endpoint. Information Protection P1 is not P2. Two Microsoft 365 licence tiers can both claim “advanced threat protection” while delivering materially different controls, and a spreadsheet comparison will not surface the difference.
The person advising you may be paid on the outcome
Most businesses buy through a reseller, and reseller margin is a percentage of spend. That does not make anyone dishonest, but it does mean the default recommendation drifts upward over time. Ask any adviser to justify a proposed Microsoft 365 licence tier against a specific requirement you can name, and treat “future-proofing” as an answer that needs evidence behind it. A recommendation you cannot trace back to an obligation is a recommendation you should test.
The decision carries a multi-year tail
Licensing is bought on annual terms, renewed almost automatically, and rarely revisited. A Microsoft 365 licence chosen carelessly in year one is usually still in place in year four, with headcount doubled and the original reasoning forgotten. The cost of getting it wrong compounds quietly rather than arriving as a single bad invoice.
What Microsoft 365 Business Premium Actually Includes
Business Premium is the most under-appreciated product in the range. It is aimed at organisations up to 300 seats and bundles a security stack that surprises people who assume Enterprise means better.
The productivity layer everyone expects
Desktop, web and mobile Office apps, Exchange Online mailboxes, SharePoint, OneDrive and Teams all come as standard. For the overwhelming majority of users this layer is identical across every Microsoft 365 licence tier discussed here, which is precisely why comparing on productivity features tells you nothing useful.
The security layer buyers often overlook
Business Premium includes Microsoft Entra ID P1 for conditional access and self-service password reset, Intune Plan 1 for device management, Defender for Office 365 Plan 1 for email threat protection, and Defender for Business for endpoint detection and response. That is a genuine, coherent security stack. Many businesses on this Microsoft 365 licence have never switched half of it on.
Windows upgrade rights and the seat ceiling
The plan carries Windows 11 Business upgrade rights, which cover most small-business needs without a separate operating system purchase. The hard constraint is the 300-seat cap. Business Premium subscriptions cannot exceed 300 users, and that single number resolves the Microsoft 365 licence question for a large share of businesses before any feature comparison begins.
What E3 Adds Above Business Premium
E3 is the enterprise baseline. It is built for organisations that have outgrown the Business family, and its advantages are structural rather than dramatic.
Scale, mailbox size and Windows Enterprise
There is no seat cap. Mailboxes are larger, archiving is more generous, and you get Windows 11 Enterprise rather than Business — which brings features such as Credential Guard, DirectAccess, and the enterprise servicing options large estates depend on. If you are past 300 people, this Microsoft 365 licence is effectively the floor.
Compliance and records management
E3 introduces meaningful data governance: retention policies, litigation hold, manual sensitivity labelling and core eDiscovery. For regulated sectors and businesses with real records obligations, these are the capabilities that make an enterprise Microsoft 365 licence defensible to an auditor.
Virtual desktop and deployment tooling
E3 includes Azure Virtual Desktop and Windows 365 licensing rights, shared computer activation, and Universal Print. None of these matter to a twenty-person firm. All of them matter to an organisation running hot-desks, contractors or a hybrid estate at scale.
What E3 Quietly Takes Away
This is the part almost nobody is told, and it is the single most expensive misunderstanding in Microsoft licensing.
No Defender for Office 365
E3 includes Exchange Online Protection — anti-spam and basic anti-malware — but not Defender for Office 365. Safe Links, Safe Attachments and anti-phishing policies are not part of it. Business Premium includes Plan 1 of that product as standard. Upgrading your Microsoft 365 licence from Business Premium to E3 therefore removes your email threat protection unless you buy it back.
No endpoint detection and response
E3 does not include Defender for Endpoint at any plan level. Business Premium includes Defender for Business, which delivers endpoint detection and response for smaller estates. A business that grows past 300 seats and moves to E3 will lose its EDR coverage on the day the migration completes, which is a genuinely serious outcome for a cybersecurity posture that was previously adequate.
Why growing businesses get caught
The trap is that the move looks like an upgrade. The invoice goes up, the plan name sounds more serious, and the security regression is invisible until an incident. Any competent review of a Microsoft 365 licence change should map the outgoing controls against the incoming ones item by item, not by tier name.
What E5 Adds on Top of E3
E5 is not simply “E3 with extras”. It is a consolidated security and compliance platform that replaces several products businesses often buy separately.
The Defender suite, end to end
E5 brings Defender for Office 365 Plan 2, Defender for Endpoint Plan 2, Defender for Identity and Defender for Cloud Apps. Together these cover email, devices, on-premises identity and SaaS usage under one console with shared signals. For an organisation that would otherwise buy three vendors, this is where an E5 Microsoft 365 licence starts to justify itself.
Entra ID P2 and identity risk
Risk-based conditional access, Identity Protection and Privileged Identity Management arrive with E5. PIM alone — just-in-time elevation of administrative rights with approval and audit — is a control that security questionnaires and cyber insurers increasingly ask about directly.
Purview, insider risk and advanced eDiscovery
Automatic sensitivity labelling, advanced data loss prevention, insider risk management, communication compliance and eDiscovery Premium sit at this tier. If your legal or compliance function has ever run a document collection exercise by hand, this is the Microsoft 365 licence that removes that work.
Power BI Pro and Teams Phone
E5 includes Power BI Pro and Teams Phone with audio conferencing. If you already pay for both separately, subtract those costs before comparing tiers — they materially change the arithmetic for finance and operations-heavy businesses.
The 300-Seat Cap and When Your Microsoft 365 Licence Must Change
The cap is the most common forcing function in this decision, and it is widely misunderstood.
What the cap actually restricts
The 300-seat limit applies to Microsoft 365 Business subscriptions — Basic, Standard and Premium — individually. It is not a limit on how many people can be in your tenant. You cannot hold 301 Business Premium seats, but you can hold 300 alongside other plan types.
Mixed tenants are entirely supported
A single tenant can carry Business Premium, E3, E5 and frontline plans simultaneously. Microsoft supports this and many organisations run it deliberately. The practical constraint is administrative: every Microsoft 365 licence type you introduce adds a policy set somebody has to maintain.
Planning the crossover properly
If you expect to cross 300 seats within eighteen months, plan the transition before you get there rather than during a hiring push. That means deciding in advance whether E3 plus the Defender products you lose is genuinely cheaper than E5, and budgeting for the migration work rather than discovering it at renewal.
What No Microsoft 365 Licence Gives You
Every tier shares the same set of exclusions, and the gap between what customers assume and what Microsoft actually undertakes is where most real-world losses happen.
Backup is not included at any tier
Retention policies, litigation hold and the recycle bin are not backup. They protect against some deletions for some periods under some configurations. Microsoft operates a shared responsibility model in which the platform is their obligation and the data is yours. No Microsoft 365 licence, including E5, includes a third-party-grade backup with independent retention and point-in-time restore.
Someone still has to operate it
E5 ships an enormous amount of capability switched off or set to default. Unconfigured Defender policies protect nothing. The most common outcome of an ambitious licensing purchase is an expensive Microsoft 365 licence delivering the security posture of a cheap one, because nobody was funded to configure and monitor it.
Everything outside the Microsoft estate
Your line-of-business application, your accounting package, your CRM and your website sit outside all of this. Defender for Cloud Apps can give visibility into sanctioned SaaS usage at the E5 tier, but visibility is not protection and it does not extend to systems Microsoft has never heard of. A Microsoft 365 licence secures the Microsoft estate well and the rest of your business not at all, which is why licensing decisions should never be mistaken for a security strategy.
Training and adoption are not in the box
Sensitivity labels only work if people apply them. Conditional access only holds if exceptions are governed. The technology is licensed; the behaviour is not.
The Real Cost of Each Microsoft 365 Licence Over Three Years
Pricing changes and varies by region, so treat the figures below as ratios for sanity-checking a quote rather than a price list. Confirm current list prices before you commit.
Indicative UK list prices
At the time of writing, annual-commitment list pricing sits broadly around £17–£19 per user per month for Business Premium, £30–£33 for E3, and £48–£53 for E5, excluding VAT. Expressed as ratios, E3 costs roughly 1.8 times Business Premium and E5 roughly 2.8 times. Those multiples have been reasonably stable and are the most useful part of any Microsoft 365 licence comparison.
The three-year picture for fifty users
At fifty seats and thirty-six months, Business Premium lands near £32,000, E3 near £56,000 and E5 near £90,000. The £58,000 spread between the cheapest and dearest Microsoft 365 licence is not a rounding difference — it is a hire, or a security programme, or a year of managed service.
The add-on route most buyers miss
E3 customers can buy the E5 Security add-on, which brings the Defender suite and Entra ID P2 without the compliance and analytics components. For a business that needs the security half of E5 but has no eDiscovery or insider risk requirement, this route frequently lands several pounds per user per month below full E5 and is the most overlooked option on the menu.
Costs that never appear on the quote
Migration effort, policy design, helpdesk load during rollout and the ongoing administration of whatever you buy are all real and none are licensed. A Microsoft 365 licence uplift with no corresponding operational budget usually delivers the invoice without the benefit.
Mixing Licences Instead of Buying One Tier for Everyone
Uniform licensing is administratively simple and financially wasteful. Very few businesses genuinely need every user on the same plan.
Not every user carries the same risk
Your finance director, systems administrator and chief executive are high-value targets with access to everything. A part-time warehouse operative logging into a shared terminal is not. Matching the Microsoft 365 licence to the risk profile of the role is a legitimate, supported strategy rather than a loophole.
Frontline plans for shift and shop-floor staff
Microsoft 365 F1 and F3 exist for deskless workers and cost a fraction of the knowledge-worker plans. For retail, hospitality, logistics and manufacturing, moving the right population onto frontline plans often funds the security upgrade for the rest of the business outright.
Keeping a mixed estate manageable
The cost of mixing is complexity. Group-based licensing in Entra ID, clear naming conventions and a documented rule for which role gets which Microsoft 365 licence keep it maintainable. Without that discipline, mixed estates drift into a state nobody can audit.
How to Choose Your Microsoft 365 Licence: A Decision Framework
Work through these in order. The sequence matters more than any individual answer.
Start with headcount and trajectory
Under 300 seats with no imminent growth spike, Business Premium is the default and the burden of proof sits with anyone proposing otherwise. Above 300, or crossing it soon, the enterprise family is the only viable Microsoft 365 licence path and the question becomes E3, E3 plus add-ons, or E5.
Then map your actual obligations
List the requirements you can evidence: regulatory regimes, client contract clauses, cyber insurance conditions, tender requirements. Map each to the specific control that satisfies it. Requirements that survive this exercise justify a higher tier; assumptions that do not survive it should not.
Then price the honest alternative
Compare E5 against E3 plus the specific add-ons and third-party products you would otherwise buy, including what you already pay for Power BI, telephony and any standalone security vendor. Only when both columns contain the same capabilities is the Microsoft 365 licence comparison meaningful.
Then decide what you will actually run
Be candid about capacity. If nobody will configure insider risk management or review Defender alerts, do not fund them. A well-operated Business Premium tenant beats an unconfigured E5 tenant on every measure that matters, including cost.
Buying Terms That Change What Your Microsoft 365 Licence Really Costs
The commercial wrapper around the subscription is as consequential as the tier itself, and it is where most procurement mistakes are made.
Annual term versus monthly billing
An annual term commits you for twelve months and prices accordingly. Month-to-month flexibility carries a premium of roughly a fifth. Paying monthly on an annual term sits between the two and typically adds around five per cent. Choosing the wrong billing model can cost more than choosing the wrong Microsoft 365 licence tier.
The cancellation window is very short
Under current commerce terms, subscriptions can only be cancelled or reduced within a short window — currently seven calendar days — after the order is placed or renewed. Miss it and you are committed for the term. Diary the renewal date and review seat counts before it, not after.
Who holds the tenant matters
Buying through a reseller under the Cloud Solution Provider programme is normal and often cheaper. Confirm in writing that your organisation is the tenant owner and that licences can be transferred if you change supplier. A Microsoft 365 licence bought under someone else’s agreement can become an obstacle at exit.
Frequently Asked Questions About Your Microsoft 365 Licence
Can we mix Business Premium and E3 in one tenant?
Yes. A single tenant supports multiple plan types simultaneously, and mixing is a supported, common approach. The only hard limit is that each Business subscription caps at 300 seats. Manage assignment through Entra ID groups so the Microsoft 365 licence attached to each role stays predictable.
Do we lose anything moving from Business Premium to E3?
Yes, and this is the most important answer on this page. You lose Defender for Office 365 Plan 1 and Defender for Business. Unless you add them back, the move degrades your email and endpoint protection. Budget for the replacement controls as part of the migration, not afterwards.
Is E5 worth it for a sixty-person business?
Sometimes. It is worth it when you would otherwise buy a separate EDR product, a SaaS security tool, Power BI Pro and telephony — or when a client contract or insurer mandates controls only E5 provides. If none of those apply, the same money spent on configuring and monitoring a Business Premium tenant will produce a better outcome.
Does any Microsoft 365 licence include backup?
No. Retention and litigation hold are not backup, and this holds true at every tier including E5. Independent backup with its own retention and restore path is a separate purchase, whether from Microsoft or a third party.
What happens when we pass 300 users?
You cannot add a 301st Business Premium seat. The usual route is to move knowledge workers to E3 or E5 while placing suitable staff on frontline plans, and to plan the crossover before the hiring happens rather than during it.
Will Business Premium satisfy our cyber insurer?
Usually, yes — if it is configured. Insurers typically ask for multi-factor authentication, conditional access, endpoint protection with detection and response, patch management and controlled administrative access. Business Premium can deliver all of those. What fails an insurance questionnaire is not the Microsoft 365 licence tier but an unconfigured tenant with legacy authentication still enabled and global administrator rights handed out freely. Answer the questionnaire against your actual configuration, not the plan name on the invoice.
Can we downgrade in the middle of a term?
Generally not. Seat reductions and plan changes are constrained to the cancellation window at order or renewal. This is precisely why the renewal date deserves a calendar entry and a genuine review of what each Microsoft 365 licence in your estate is actually doing.
Getting the Decision Right
The right answer is rarely the most expensive one. For most businesses under 300 seats, a properly configured Business Premium tenant delivers a stronger security posture than a partially deployed E5, at a third of the cost. For larger organisations, the honest comparison is E3 plus targeted add-ons against full E5, priced against everything else you would stop buying.
What matters is that the choice is made deliberately, reviewed at renewal, and matched to obligations you can actually evidence. A Microsoft 365 licence decision taken on a reseller’s recommendation and never revisited is how businesses end up paying enterprise prices for small-business outcomes — or, more dangerously, running a growing organisation on protection that quietly stopped being adequate two years ago.
