Microsoft 365 is sold by the seat. One person, one license, billed monthly, on a term you commit to up front. That sounds simple, and for the first 20 people it usually is. The complexity shows up later, in the places where a license is required but nobody told you, or where a decision you made at signup quietly locks in your spend for a year.
This is a walkthrough of how the licensing works, what changes your bill, and where the traps are. Every claim below links to Microsoft's own documentation. We quote no prices anywhere, because prices change and regional variation is real. Current figures live on Microsoft's business plans page and enterprise plans page.
The Business family, and the ceiling you will eventually hit
Most small and midsize companies buy from the Business family. There are three plans that matter.
| Plan | What you get |
|---|---|
| Business Basic | Web and mobile versions of Word, Excel, PowerPoint, and Outlook. Business email, 1 TB of personal cloud storage, and Teams. No installed desktop apps. |
| Business Standard | Everything in Basic, plus the installed desktop versions of the Office apps on Windows and Mac. |
| Business Premium | Everything in Standard, plus device management, identity protection, threat protection, and information protection. |
The ceiling: Microsoft caps the Business family at 300 seats across all three plans combined, per tenant. If you have 250 Business Premium seats, you can add 50 more seats of any Business plan and that is it. Microsoft states plainly that it reserves the right to enforce this limit, and there is no process to raise it.
What this means for your money: if you are at 240 people and hiring, start pricing the crossover now. Moving 300 people to a different plan family under time pressure is a worse negotiation than planning it two quarters out.
What Business Premium adds over Standard
Business Premium is the same productivity software as Standard with four capability groups layered on. In business terms:
- Device management. Microsoft Intune lets you require a passcode, encrypt the disk, push updates, and remotely wipe company data from a laptop or phone. Without it, a lost laptop is a phone call to the person who has it.
- Identity protection. Business Premium includes Microsoft Entra ID P1, the paid tier of Microsoft's identity service (this is the product formerly called Azure Active Directory). The practical feature is Conditional Access, which lets you write rules like "finance can only reach payroll data from a managed device." Microsoft documents which plan includes which Entra tier.
- Threat protection. Microsoft Defender for Business protects the endpoints themselves, and Defender for Office 365 Plan 1 inspects links and attachments in email before they reach the inbox.
- Information protection. Labels and encryption you can apply to a document or an email so it stays protected after it leaves your network.
Microsoft's Business Premium documentation hub is the reference. The framing that matters for a buyer: Standard is a productivity purchase, Business Premium is a productivity purchase plus the tools to control company data on devices you do not physically hold. If everyone works on a company-owned desktop in one office, the gap is smaller. If people work from personal laptops and phones, it is large.
Enterprise plans, and when a small business genuinely needs one
The Enterprise family (E3, E5, and the newer E7) has no seat cap and adds compliance, analytics, and deeper security tooling. E3 is the baseline. E5 adds the higher tiers of the Defender products, advanced data governance and legal discovery, and Power BI Pro for reporting. Details are on the enterprise plans page.
Under 300 people, a genuine need for E3 or E5 usually comes from one of four places: you crossed the seat cap, you have a regulator or a contract that requires specific data retention and legal hold capabilities, you need mailboxes larger than 50 GB, or you want Power BI Pro across the company and the bundled price beats buying it separately. Absent one of those, Business Premium covers most of the same ground for a smaller business.
You do not have to move everyone. Mixing plan types in one tenant is supported and common. You can run 280 Business Premium seats alongside 20 E5 seats for the people who need the extra compliance tooling.
Frontline plans, and their real limits
Microsoft 365 F1 and F3 are built for staff who do not sit at a desk: shop floor, retail, warehouse, field. They are priced well below the knowledge-worker plans, and the limits are the reason. Microsoft describes the intended user types, and eligibility is contractual: these licenses are meant for people whose primary work device has a screen smaller than 10.9 inches or is shared across shifts.
The limits that matter:
- No installed desktop Office apps. Web and mobile only.
- Office 365 F3 gives a 2 GB mailbox, and archive mailboxes are not included, per Microsoft's Exchange Online limits.
- Microsoft 365 F3 gives 2 GB of personal cloud storage per user, against 1 TB on the Business plans, per the OneDrive service description.
A 2 GB mailbox is roughly a year of ordinary email for someone who receives attachments. Assigning frontline licenses to office staff to save money reliably produces a support ticket within 18 months.
Commit annually, and pay annually
Two separate choices get made at checkout, and they are routinely conflated. Term length is how long you are committed: monthly, annual, or three-year. Billing frequency is how often you are invoiced: monthly, or once up front for the year. You can hold an annual term and still be billed monthly, so choosing "annual" in one place does not automatically get you both.
For almost every business, the right answer is annual on both: an annual term, paid up front.
- The annual term costs less per seat. Month-to-month carries a premium, and that premium applies to every seat, every month, all year.
- Annual payment is less administrative work. One invoice, one approval, one entry in the accounting system, rather than 12 of each.
- It fixes your rate for the term. A price increase Microsoft publishes mid-term does not reach a commitment you have already made. On month-to-month, it reaches you at the next renewal, which is next month.
- The flexibility you give up is narrower than it looks. You can still add seats at any time on an annual term. The only thing you lose is the ability to drop seats mid-term.
The case for monthly commitment is genuinely limited: a workforce that swings hard and predictably inside the year, or a business that expects to leave the platform within 12 months. Outside those two situations, the monthly premium buys an option most companies never exercise and pay for every month regardless.
Two rules govern what you can change afterward, and both are worth understanding before you sign.
The cancellation window is seven calendar days. For subscriptions bought directly from Microsoft, you can cancel and receive a prorated refund only within seven calendar days of the subscription starting or renewing. After that, your option is to turn off automatic renewal and keep the service through the end of the term you paid for. Microsoft documents this on the cancel your subscription page. Buying through a partner works the same way, per the new commerce cancellation policy.
You can add seats any time. You generally cannot drop them until renewal. Seat reductions are only possible inside that same seven-day window, and the window applies separately to each purchase: at signup, at renewal, and when you add seats mid-term. Add 15 seats in March on an annual term, and by the second week of March those 15 seats are yours until the anniversary date.
What this means for your money: commit annually, pay annually, and size that commitment to the headcount you are confident about rather than the headcount you hope for. Adding seats takes about a minute. Removing them waits for the anniversary.
How you buy, and why it changes your support experience
There are three common purchase routes.
- Direct from Microsoft. You pay Microsoft with a card or invoice, and you open support tickets with Microsoft. Simplest path, no intermediary, no help interpreting what you bought.
- Through a Cloud Solution Provider partner. A partner resells the licenses, bills you, and typically becomes your first line of support. Microsoft describes the partner relationship types, including granular delegated administration, which lets a partner do specific admin work without holding full administrator rights in your tenant. Worth asking any partner which model they use.
- Enterprise Agreement. A negotiated volume contract, generally aimed at larger organizations. Rarely the right fit under 300 seats.
One practical consequence: a few purchases can only be made in certain channels. Extra SharePoint storage, for example, cannot be bought directly from Microsoft if your subscription came through a partner or volume licensing. You go through your partner instead.
Nonprofit and education pricing
If you are a registered nonprofit, a public library, or a public museum, you likely qualify for granted (free) and discounted licenses. Microsoft publishes its eligibility criteria, and the current offer includes a quantity of granted Business Basic seats plus substantial discounts on the paid plans. Two rules catch people: grants are restricted to paid employees and unpaid executive leadership, while discounts extend to volunteers and general staff, and the offers change. The Business Premium grant that many nonprofits relied on was discontinued and replaced with discounted pricing. Check the current nonprofit plans rather than assuming last year's arrangement still holds.
Schools and universities buy from a separate Microsoft 365 Education lineup (A1, A3, and A5). Businesses cannot buy education pricing, and nonprofit eligibility explicitly excludes schools and government agencies.
One more line item: Teams
Since April 2024, Microsoft has sold new Enterprise subscriptions without Teams included. New Enterprise customers buy a "no Teams" suite plus a separate Microsoft Teams Enterprise license. The Business plans are still available in both versions, with and without Teams. Microsoft explains the change on its licensing news page. If you are quoting a new tenant, confirm whether Teams is in the quote or beside it.
Gotchas that catch non-technical buyers
These are the items that produce surprise invoices and surprise data loss. None of them are obvious from a pricing page.
Shared mailboxes are free until they are not
A shared mailbox (info@, support@, billing@) does not need its own license. It holds up to 50 GB. Cross 50 GB and it stops sending, then stops receiving, and senders start getting bounce messages. To go past 50 GB you must assign it a paid Exchange Online Plan 2 license. The same license is required to put a shared mailbox on legal hold or to give it a large archive. Microsoft lays this out on the shared mailboxes page.
Related: to access a shared mailbox, a person needs their own licensed mailbox. Shared mailboxes are not a way to give unlicensed staff email.
Room and equipment mailboxes are free
Conference rooms, company vehicles, and projectors booked through Outlook use resource mailboxes. Those do not require a license and are capped at 50 GB, which no conference room will ever reach. Nobody should be selling you licenses for meeting rooms.
When someone leaves, the clock is 30 days
Remove or delete a departing employee's license, and their email, contacts, and calendar are retained for 30 days and then permanently deleted. Microsoft's offboarding guide walks the sequence. Two things to do before you free up the seat:
- Convert the mailbox to a shared mailbox if colleagues or customers still email that address. It keeps working without a license, subject to the 50 GB limit above.
- Grant someone access to the departing person's OneDrive files. If you remove the license but do not delete the account, that content stays accessible past 30 days. If you delete the account, the 30-day clock starts.
The archiving and retention gotcha: if you need to keep a former employee's mail for years, for a regulator or a lawsuit, you must apply a retention policy or hold to the mailbox before deleting the account. Do that, and the mailbox becomes an "inactive mailbox" that is retained without consuming a license. Delete the account first, and after 30 days the data is gone. Microsoft is explicit that the hold must be confirmed as applied first, on its inactive mailboxes page.
Storage is two separate pools, and one of them is shared
Personal storage (OneDrive) is per user: 1 TB on Business Basic, Standard, and Business Premium, and 1 TB on E3 and E5 with the option to raise it to 5 TB. Full table in the OneDrive service description.
Shared storage (SharePoint, which is where Teams files are stored) is a single company-wide pool, calculated as 1 TB plus 10 GB per licensed user. Thirty people gives you roughly 1.3 TB for the whole business, not 30 TB. If you exceed it, your environment can be put into read-only mode. The formula and that warning are on the SharePoint limits page.
More shared storage is a separate purchase, not something that arrives with more seats. Microsoft sells it in 1 GB increments and, more recently, as pay-as-you-go capacity. See buying more storage. A company migrating a decade of files off a server should size this before the migration, not during it.
Mailbox and archive sizes differ by plan more than people expect
Per Microsoft's Exchange Online limits: user mailboxes are 50 GB on the Business plans and 100 GB on Microsoft 365 E3 and E5. The archive mailbox, a second storage area for older mail, is 50 GB on Business Basic and Standard, and up to 1.5 TB on Business Premium, E3, and E5.
That 1.5 TB comes from auto-expanding archiving, which grows the archive automatically once the initial 100 GB fills. Two caveats from Microsoft's auto-expanding archiving documentation: provisioning the extra space can take up to 30 days, and the archive is only supported for a single person's mail. Routing multiple users' mail into one archive is not permitted.
Guests are mostly free, with a real limit
Inviting an external client or contractor into a Teams channel or a SharePoint site does not consume a Microsoft 365 seat. External identities are billed on monthly active users, and Microsoft states that the core features are free for the first 50,000 monthly active users. For a business under 300 employees, guest access is effectively free.
Where it breaks: guests are guests. They cannot be given a shared mailbox, and applying advanced governance features to them (access reviews, entitlement management) moves them into paid add-on territory. Microsoft describes the billing model in detail.
Add-ons require a base license
Almost every add-on, whether that is phone service, dial-in conferencing, extra storage, or Microsoft 365 Copilot, must sit on top of a qualifying base license for the same person. You cannot buy a bare add-on for an unlicensed account. Budget the base seat and the add-on together.
Where to start
If you are looking at a renewal or a first purchase, three questions do most of the work. How many seats will you truly have on the anniversary date, not today? Do people touch company data on devices you do not own? And is there anything you are legally required to keep, and for how long?
If you would like a second read on a quote or a renewal, bring us the license list and your headcount plan for the next 12 months. We will tell you which lines are load-bearing, which are duplicated, and whether your term and billing frequency are set the way they should be.