Use this guide to reset a device and prepare it for a new user.

Note
Removing a device from on prem Active Directory is only necessary for Hybrid AD devices.

Removing a Device from Users and Computers (Active Directory on Prem)

This is only applicable if the device was Hybrid AD. If it is not then you can move onto the next section.
Open Active Directory Users and Computers
Right click on “co.ssd.k12.mo.us” and select Find…
Type in the Computer name of the object you’re looking for
Right click on that object and delete it

Removing a Device from Endpoint Manager and Autopilot

You will use Azure AD and Endpoint Manager for the next steps

Google Chrome or Microsoft Edge is the best browsers to use for this.

Record the serial number of the device that needs to be removed.
1. In my example you'll find that I'm working on device 5X38M63.
Log into Office 365.
Either using the tiles to the left of your screen or select the "Waffle" in the top left to get a list of options to chose.
Select the Admin Tile.
The tile looks like this and will open a new screen:
Select "Show All" on the left menu area.
Select "Endpoint Manager".
Chose "Devices" on the left panel.
Chose "Windows".
You can search for the device by its Serial Number.
Select the record you want to work with.
In most cases the name of the records should match between Endpoint Manager and Azure AD
Select the Delete option (Looks like a trash can).
Select "Yes" when asked to confirm deleting the record.
Next we'll need to remove the Autopilot record from MEM.
Click Devices.
Click Enroll DevicesEnrollment.
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Under "Windows Autopilot Deployment Program" select Devices.
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Put the serial number of the device you want to check up on here.
Check the box to the left of the box of the device we want to remove.
Click the "Delete" option.
Select the "Yes" option to confirm the operation.
If you click the bell icon you can see the status of the deletions taking place. Autopilot deletion will take several minutes. You don't have to wait. You can move onto the next step.

You may skip the first few steps if you know how to navigate to Azure Active Directory.

Log into Office 365.
Either using the tiles to the left of your screen or selecting the "Waffle" in the top left look for the Admin tile.
Select the Admin Tile.
The tile looks like this and will open a new screen:
Select "Show All" on the left menu area.
Select "Azure Active DirectoryIdentity".
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You will select "Azure Active DirectoryDevices" again on the panel on the left.
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Select "All Devices".
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Search for the device name. In my case I'm looking up SSD-5X38M63. In most cases (While we're in a Hybrid environment) If the device is a Hybrid AD device there will be two resultsrecords like shown below. If its not there will only be one record.
Select all matching device records.
When you do this the trash can icon with the selection "Delete" will be available. Chose this.
If the records do not delete then its likely there's something connected to MEM still.