SharePoint went read-only after you ran over storage: "Confirm purchase", what actually frees space, and what Learn does not tell you

The tenant is over its SharePoint storage limit, sites are read-only, and someone has already bought storage. The banner is still there. This article sets out what Learn says about getting out of read-only, what the "Confirm purchase" button does and does not do, what really frees space fastest, and the one thing Learn leaves out for commercial tenants: how long you have before the lock.

What read-only means, and what causes it

The SharePoint limits page says a tenant that keeps operating above its storage limit risks being put into read-only mode, where users may be unable to add or modify content until usage is reduced or capacity is purchased. The out-of-storage troubleshooting page shows the two admin emails that go with it: "SharePoint Online is out of storage space. Sites are in read-only mode and changes can't be saved", and "Your storage is full. You can buy more storage or use Microsoft 365 Archive to free up storage space without deleting any data." The storage planning page adds that when the quota is exceeded, classic site creation and site creation through PowerShell is blocked.

The limit is the tenant pool: 1 TB plus 10 GB per eligible licence, plus any Office 365 Extra File Storage you bought, in binary gigabytes (1 GB = 2³⁰ bytes). A tenant with 100 eligible licences has 1,024 + 1,000 = 2,024 GB. See the pool article for which licences count. Archived data lives in SharePoint but does not count toward the active quota, and sites in the recycle bin do not count either.

The three ways out, in Learn's words

The footnote on the limits page names them: reduce storage usage, purchase additional SharePoint storage, or purchase eligible licences. The troubleshooting page lists the same three in its own terms: buy add-on storage or extra licences, archive inactive content that must be kept, or delete content that is no longer needed.

"Confirm purchase": a bridge, not a fix

If you have completed a purchase and Confirm purchase is offered, selecting it temporarily removes read-only mode for up to 14 days while the new capacity is applied. It can be used only once in a 365-day period. Three things follow from that wording.

• It is a one-shot. If the first purchase is too small, or the pool is still over after it lands, a second Confirm purchase inside twelve months is not available. Size the purchase against current usage plus a margin before you click anything.
• It is conditional. The button appears only when a purchase is complete and Learn says "if" it is available. Learn does not say what to do when it is not offered.
• It lifts the lock for up to 14 days. It does not say how long capacity takes to apply, only that the window is up to 14 days. If you are still locked after buying, look at the billing side first: is the purchase complete, is the licence assigned, is the add-on on the same agreement as the tenant?

How long before the lock

For commercial tenants Learn gives no day count. It says "risk of ... read-only mode" and nothing about a grace period. Education tenants are different: the Education pooled-storage guidance says that at 100% of the pool the tenant has 30 days to act before OneDrive and SharePoint go read-only, and that a pooled limit can take up to 48 hours to reflect new purchases. If you are a commercial tenant and relying on a grace period you cannot find in writing, treat usage at the limit as the deadline.

What frees space fastest

Order matters, because three of these are slow and one is not.

1. Archive inactive sites. Microsoft 365 Archive moves a site out of the active quota. The troubleshooting email offers it as a way to free space "without deleting any data". It is billed at $0.05/GB/month, a quarter of the $0.20 active rate, so it frees quota and costs less than buying the same capacity as active storage. It does not need a retention conversation.
2. Empty the recycle bins. Learn says the space a site recycle bin uses is part of the organization's total storage limit, and recommends monitoring the bins and emptying them regularly. Deleted files keep counting until the bin is emptied or they age out.
3. Trim version history. Versions often exceed the live files. Changing the limit does not reclaim what already exists; a trim job does, and it only reaches versions that no retention policy covers. The version-trimming article has the detail. The storage planning page also notes that trimming does not touch the Preservation Hold library, because the original copies are preserved.
4. Check Preservation Hold. A site under retention keeps a copy of deleted and changed files in a hidden library that counts toward the quota. On those sites, deleting does not free space until the retention period ends and the clean-up job runs. Do not promise a deletion drive until you know which sites are under retention.

Which route, by size of the overage

Two details on the meter. While a tenant is enrolled in pay-as-you-go SharePoint storage, it is considered within quota, so you stop getting quota emails and admin-centre banners. Set an Azure budget with alerts, because the warnings you used to rely on are gone. And if you disconnect pay-as-you-go while over quota, enforcement resumes immediately. As of the 13 October 2026 Learn text, pay-as-you-go SharePoint storage is in public preview for commercial tenants and is not available to Education, GCC or 21Vianet. Office 365 Extra File Storage cannot be bought directly from Microsoft if the subscription came through Volume Licensing or a CSP.

A sequence for the day it happens

1. Open the SharePoint admin centre, Active sites, and read the storage bar. Remember it excludes the last 24 to 48 hours.
2. Run Learn's storage diagnostic from the out-of-storage page. Learn says it identifies any issues that affect your SharePoint storage quota and shows how the quota is allocated.
3. List the ten biggest sites and split each into live files, versions, recycle bin and Preservation Hold. The audit article has the commands.
4. Decide the purchase size from current usage plus margin. Remember Confirm purchase works once a year.
5. Buy, then use Confirm purchase if it is offered, and write the date down. The 14 days is the working window for the rest of the fix.
6. Archive and trim inside those 14 days so the next month does not repeat the lock.
7. Tell users it is read-only by design and what is being done. Silence reads as an outage.

Disclosure: StorageScout is our product. Prices are Microsoft's public US list prices as documented on Microsoft Learn at the time of writing; your agreement, region and currency may differ. Reports from admins about delays after purchase are forum anecdotes, not Microsoft statements. StorageScout is independent and not affiliated with or endorsed by Microsoft.

Sources

• SharePoint limits — pool formula, read-only risk, three ways out, Confirm purchase (up to 14 days, once in 365 days)
• SharePoint Online out of storage space — the two admin emails, archived data not counted, diagnostic tool, options
• SharePoint storage planning — what happens over quota, trimming and the Preservation Hold library, deleted sites, 48-hour lag
• Add more OneDrive and SharePoint storage — pay-as-you-go SharePoint Storage, in-quota behaviour, disconnect, Extra File Storage and CSP limits
• Manage site storage limits — storage figures exclude the last 24 to 48 hours
• Pay-as-you-go pricing — Storage services — $0.20/GB/month active, $0.05/GB/month Archive
• Pooled storage management (Education) — the 30-day grace period that applies to Education only