Microsoft 365 backup: what Microsoft keeps and what backup costs

What does Microsoft keep, and for how long?

Microsoft keeps deleted items for set periods so you can undo mistakes. Teams channel files live in SharePoint, so the SharePoint window applies.

• 14 daysDeleted email, by default. An admin can raise it to 30.
• 93 daysDeleted files in the OneDrive and SharePoint recycle bin.
• 30 daysA deleted mailbox, before it is gone for good.
• 30 daysA leaver's OneDrive, by default (30 to 3,650).

Retention policies and litigation hold (in Business Premium, Office 365 E3 and E5, and Microsoft 365 E3 and E5) stop content being permanently deleted, but Microsoft says they are built for export, not mass restore. See which plans include them.

What is Microsoft 365 Backup, and what does it cost?

Microsoft 365 Backup is Microsoft's own backup for Exchange mailboxes, OneDrive and SharePoint (Teams chats aren't covered). It's a pay-as-you-go add-on for any Business, Enterprise or Frontline plan, billed through an Azure subscription at $0.15 per GiB a month. You choose how long backups are kept: 3 months to 10 years for OneDrive and SharePoint, and up to 2 years for Exchange. Restores are free, and data stays inside Microsoft 365.

Cost calculator

Microsoft 365 Backup cost calculator

Enter the total you'll protect: mailboxes with archives, OneDrive and SharePoint. Prices are ex VAT.

Data to protect

Unit

GB TB

Work it out for me

Fill in what you know and the total above updates. Sizes are in the Microsoft 365 admin centre under Reports › Usage; online archives and second-stage recycle bins aren't in those reports.

Usersincluding shared mailboxes

Mailbox plus archiveaverage GB per user

GB

OneDriveaverage GB per user

GB

SharePointGB, all sites

GB

Deleted items and older versionsoptional, GB you have measured

GB

Adds up to 0 GB.

£116.74 a month

£1,400.83 a year for 1 TB (1,024 GB). Indicative pounds, ex VAT. US list price $153.60 a month ($1,843.20 a year).

Include deleted items and older versions in your total: Microsoft bills them too, and publishes no typical figure.

Get vendor-neutral quotes

How this is worked out

Protected data = users × (mailbox and archive + OneDrive) + SharePoint + deleted items and older versions.

Cost = protected GiB × Microsoft's list price of $0.15 a month. A year is 12 months with no growth, as in Microsoft's own calculator.

Microsoft lists Microsoft 365 Backup at $0.15 per GiB a month and doesn't publish a sterling price. Sterling figures use the rate Microsoft's Azure price list shows for UK regions (£0.0038 per GB a day, which we treat as per GiB), which Microsoft describes as an estimate. Your Azure invoice converts the US dollar price at Microsoft's monthly exchange rate. Prices exclude VAT.

We treat GB as GiB, as Microsoft's calculator does, so decimal GB figures overstate the cost by up to about 7%. Restores are free, with no other Azure charges. Prices through a CSP partner or an Azure agreement can differ.

Your Microsoft 365 plan is priced separately: see Microsoft 365 pricing in the UK.

What is an immutable backup, and why does it matter?

An immutable backup can't be changed or deleted until its retention period ends, even by an administrator. It matters because an attacker with an admin account can delete ordinary backups before striking.

Microsoft 365 Backup is partly immutable: backups can't be altered, but an admin can delete them by offboarding (with a 90-day undo) or shorten how long they're kept (after 30 days).

Ask any provider:

1. Can anyone, including our admins, delete backups or shorten retention early?
2. Do deletions need a delay or a second approver, and can they be undone?
3. Can we restore an older, clean copy if recent backups are encrypted?
4. How are we alerted to mass deletions, even if our systems are compromised?

These follow the NCSC's Principles for ransomware-resistant cloud backups (November 2024).

How do Microsoft 365 Backup, Acronis, Spanning and Veeam compare?

Third-party backup software can keep copies outside Microsoft's service. This compares three on facts from each vendor's own pages. It doesn't rank them or show prices.

What each product's own documentation says, checked 31 October 2026. Tap a product to open it.

Listed in alphabetical order after Microsoft's own product; inclusion isn't a recommendation. Checked against each vendor's documentation on 31 October 2026. Vendors change their products often, so confirm before you buy.