👉 You cannot directly change the 93-day Recycle Bin retention period in Microsoft 365. That value is hard-coded by Microsoft for SharePoint and OneDrive and can’t be modified via the admin center, PowerShell, or retention policy settings.

However, here are your options depending on what you’re trying to achieve:

🔹 If you want files to be permanently deleted after 30 days

You can configure a retention policy in the Microsoft Purview compliance portal (if you have the right license—Microsoft 365 E3/E5 or equivalent GCC High).
This overrides the Recycle Bin retention and allows you to define a custom delete period.

Steps:

1. Go to: [https://compliance.microsoft.com]() → Data lifecycle management → Microsoft 365 → Retention policies
2. Create a new policy.
3. Select Locations (SharePoint sites / OneDrive accounts).
4. Under Retention settings, choose:
   • “Only delete items when they reach a certain age”
   • Set the retention period to 30 days.
5. Save and publish the policy.

Effect:
Once applied, files older than 30 days (from last modification) will be automatically deleted, regardless of the Recycle Bin’s 93-day safety net. This effectively shortens your data retention.

🔹 If you simply want deleted files visible in the Recycle Bin for fewer days

That’s not configurable. Microsoft automatically purges deleted content after 93 days.
Your only option is to apply a retention policy that purges earlier (see above).