Cancelling & Terminating A Microsoft 365 Tenancy
Login to the admin center of Office 365. https://admin.microsoft.com/#/homepage
Click on the hamburger icon in the top left.
Click "Billing" then "Your products".
Under each license, click "Cancel subscription", such as for MS Business Basic, Standard, Premium and whatever else you have.
Choose "Cancel now".
Press "Next".
Give a reason, normally just "Didn't use" or whatever else.
Click "Cancel now".
If you then click into the subscription name, you will see at the top "Subscription status" as "Disabled".
There is additionally a "Cancel" button here. Sometimes it appears and sometimes it doesn't.
Check back later and click on this button if you are missing it at the moment.
Click back onto the hamburger icon in the top left and click on "Identity".
When Identity loads (Azure AD), click on "Manage tenants" along the top.
Tick the organization along the left (Your tenancy name) and click "Delete" on the top bar.
We now need to make all the warning triangles green ticks so you can then permanently delete the tenancy. Without them all ticked, Microsoft just doesn't let you bin the tenancy.
The action "Get permission to delete Azure resources" is really easy to change. Click the blue text in the action column and turn the toggle on from No to Yes when it opens the new page. Make sure you press "Save" in the top right corner. You will get a notification when it's done in the top right.
To go back to the delete tenancy page, click the blue "Delete tenant...?" address bar header.
You can click "Refresh" along the top bar to check each stage is complete.
For "Delete all license-based subscriptions", this will take you to the documentation pages of Microsoft on how to disable and delete the licenses, but close this as we've already done it in the admin center earlier on.
When you think you have completed them all and waited for your licenses to expire, you can then delete the tenancy by pressing the delete tenant again at the bottom of the screen.