14.4 Base Licensing vs Add-on Licensing

Quick Answer: Base license = the suite that gives the user core Microsoft 365 / Office 365 services (Business Basic / Standard / Premium, Microsoft 365 E3 / E5, F3). Add-on = an extra product that requires a qualifying base on that same user — Microsoft 365 Copilot, Teams Phone or Audio Conferencing when the suite does not already include them, many Defender / Purview packs, extra storage. You almost never assign “Copilot only” to a person with no Microsoft 365 or Office 365 base.

The April 30, 2025 outline asks you to describe the differences between base licensing and add-on licensing. This is the companion to “assign the seat” in section 14.3. The admin center will happily list both a suite and a Copilot add-on. The exam asks whether the second one can stand alone.

What a base license is

A base license (Microsoft also says suite, plan, or qualifying subscription) is the product that entitles a user to the core work platform: sign-in with a work account, and — depending on the plan — Exchange mail, Teams, SharePoint, OneDrive, and Microsoft 365 Apps for the web or desktop.

Official service-description families you should be able to name:

Office 365 E1 / E3 / E5 remain living base suites for organizations that want the productivity cloud without the Windows + Intune bundle that Microsoft 365 enterprise plans add. Chapter 2 already taught that name split; here it matters because an Office 365 E3 user still has a qualifying base for many add-ons even though they do not have Windows Enterprise from that SKU.

Microsoft’s plan-options article is explicit: several plans have add-ons you can buy for the subscription, and you can mix Enterprise, Business, and standalone plans in one tenant. The 300-user cap is a tenant-wide Business-family limit (Basic + Standard + Premium + Apps for business together), not “300 of each.” Organizations above that line should be on enterprise (or frontline) plans.

Standalone services such as Exchange Online Plan 1 or Microsoft 365 Apps for enterprise can act as a narrow base for people who only need mail or only need desktop apps. They are still bases, not add-ons, when they are the thing that qualifies the user.

What an add-on is — and why the base must already be there

An add-on license adds a capability that is not in the user’s current suite, or not in enough quantity. Official Learn pages keep repeating the same dependency: the add-on is sold to organizations that already have a qualifying Microsoft 365 or Office 365 subscription, and it is assigned to a user who already has that base.

Verified examples you can use on the exam:

• Microsoft 365 Copilot — Microsoft’s licensing article states Copilot is available as an add-on plan with listed prerequisites. Qualifying bases include Microsoft 365 Business Basic / Standard / Premium, Microsoft 365 E3 / E5 / F1 / F3, Office 365 E1 / E3 / E5 / F3, and several workload-only plans (Exchange, SharePoint, Teams, and others). Copilot Chat web grounding can be included with an eligible Microsoft 365 subscription at no extra Copilot add-on; work-grounded Copilot in the Microsoft 365 Apps is the add-on story. You still assign Copilot like any other license — after the base exists.
• Microsoft Teams Phone Standard (historically Phone System) — official Teams add-on licensing lists prerequisite licenses: Business Basic / Standard / Premium, F1 / F3, E3, Office 365 F3 / E1 / E3, or a standalone Teams license. E5 includes Phone System; those users do not buy Phone System again just to get PBX features. Calling Plans are a further add-on for PSTN minutes.
• Audio Conferencing — official Teams documentation: included in E5; still a separate add-on for Microsoft 365 or Office 365 E1 or E3 (and available as an add-on on Business Standard and similar). It does not require a Teams Phone license.
• Defender and Purview add-ons — organizations on E3 or Business Premium often buy security or compliance packs instead of jumping the whole workforce to E5. Official Purview service-description language states some add-ons require a Microsoft 365 Business Premium base and are capped at 300 seats. That is the add-on pattern: qualifying base + extra SKU + assignment.
• Extra storage — OneDrive Extra Storage is purchased and then assigned to a licensed user like any other add-on. Office 365 Extra File Storage adds SharePoint tenant capacity in 1 GB increments for eligible plans. If the add-on does not appear, the plan is not eligible — another way of saying “no qualifying base.”

The exam sentence: you cannot usually assign only the add-on with no qualifying base. The admin center and Partner Center enforce prerequisites. “We bought 50 Copilot licenses and assigned them to people with no Microsoft 365” is the trap.

Some capabilities are add-ons on one suite and included on another. Audio Conferencing and Phone System on E5 versus E3 is the cleanest official illustration. Power BI in E5 versus not in E3 is another. Do not memorize an unofficial 200-row matrix; learn the pattern.

E3 vs E5 vs Business Premium vs F3 — conceptual, not a price list

MS-900 will paraphrase “which plan?” using job + risk + company size, not a dollar amount. Stay with official comparison themes:

• Business Premium is the small-business base that already includes Intune, Defender for Business, Entra ID P1, and Azure Information Protection. Choose it when the company is inside the 300-user Business family and needs endpoint management plus SMB-grade threat protection without an enterprise agreement. It is not E5. It does not include the full Microsoft Defender XDR / Purview E5 stack.
• Microsoft 365 E3 is the enterprise baseline base: unlimited users, Windows Enterprise, Intune Plan 1, desktop Microsoft 365 Apps, Exchange Plan 2 (larger mailboxes and archiving compared with Business / Plan 1). Security and compliance are solid but not the E5 suite. Voice (Phone System, Audio Conferencing) is typically an add-on.
• Microsoft 365 E5 is the enterprise deep suite: Microsoft 365 Defender suite (Defender for Office 365 Plan 2, Defender for Endpoint, Defender for Identity, Defender for Cloud Apps, and related capabilities), Microsoft Purview suite (premium eDiscovery, insider risk, customer lockbox, privileged access management, and related capabilities), Phone System, Audio Conferencing, Power BI, and Entra ID P2. Calling Plans are still extra if you want Microsoft as the PSTN carrier.
• Microsoft 365 F3 is a frontline base: shift workers, retail, factory, clinical floors. Official limits to remember: Exchange Online Kiosk (not a full E3 mailbox), 2 GB OneDrive, no desktop Microsoft 365 Apps (web and mobile), no Power BI in the suite, no Azure Information Protection in the suite. F3 still includes Teams and SharePoint so a frontline worker can collaborate. Microsoft 365 F1 is even lighter (no Exchange mailbox entitlement). Frontline Phone add-ons exist and require a frontline base.

Upgrade paths stay inside or across families: Basic → Standard → Premium, E3 → E5, or Business → Enterprise when you outgrow 300 users. You can also mix F3 for the plant floor with E3 for headquarters in one tenant. That mix is still base + base, not add-on chaos.

Do not invent suite list prices. Public marketing pages show per-user monthly figures that vary by country, commitment, and whether Teams is bundled. The exam scores what is in the box and what requires a prerequisite, not a checkout total.

Realistic exam-style scenarios

Copilot for finance analysts. They already have Microsoft 365 E3. Buy the Copilot add-on and assign it to those E3 users. Do not assign Copilot to a contractor who has no Microsoft 365 or Office 365 base.

Dial-in numbers for E3 meeting organizers. That is Audio Conferencing as an add-on. If the same company were on E5, Audio Conferencing is already in the base.

Retail clerks on shared handhelds. Microsoft 365 F3 is the frontline base. Adding Teams Phone Standard for Frontline Workers still requires that frontline base. Do not buy enterprise E5 for every cashier unless the scenario actually needs the E5 stack.

80-person company, laptops must be managed, mailbox malware is a concern, they will never exceed 300 users. Business Premium is the base that already includes Intune and Defender for Business. They can still add Copilot or extra storage. They should not be told they “must buy E5 or they cannot use Intune.”

SharePoint is full. Extra File Storage is an add-on capacity product for eligible tenants — not a second E5 for every user.

Exam traps

• Add-on without a base usually fails. Copilot, Teams Phone, and most security packs need a qualifying suite on the user.
• Included ≠ add-on. Phone System and Audio Conferencing are in E5; they are add-ons on E3.
• Business Premium is not E5 and F3 is not a cheap E3. Size, mailbox, storage, desktop apps, and security depth all differ.
• The 300-user cap is the Business family, not a secret enterprise limit.
• Standalone Exchange or Apps can be a base for some add-ons — do not insist that only E5 qualifies Copilot.
• Do not recite unofficial price lists. Channel and country change what finance pays.
• Mixing bases in one tenant is allowed. Frontline F3 plus enterprise E3 is a normal design.

Official sources

• Microsoft 365 and Office 365 plan options — Business 300-user cap; service availability; add-ons; mixing plans
• License options for Microsoft 365 Copilot — Copilot as an add-on with listed prerequisites
• Microsoft Teams add-on licenses — Audio Conferencing and Teams Phone prerequisites; E5 inclusion
• Teams Phone licensing — prerequisite licenses for Teams Phone Standard
• Add storage space — OneDrive Extra Storage assigned like an add-on; Extra File Storage in 1 GB increments
• Microsoft Purview service description — some add-ons require a Business Premium base
• Microsoft Intune licensing — Intune Plan 1 in Microsoft 365 E3 / E5 bundles
• Study guide for Exam MS-900 — base licensing versus add-on licensing