Salesforce doesn't allow the deletion of Users, for data integrity purposes. What you do in this case is deactivate the User (active checkbox) which frees up your licenses.
Unfortunately, the Salesforce accounts once created can't be deleted, but you can deactivate it. If you want to create a new account with the same username first change existing account username and use this username for a new account.
Note: You can't deactivate the username of the system administrator. If you want to deactivate system administrator, please email us at trailhead@salesforce.com and we can assist with account deactivation.
Hope this helps you! Please feel free to reach us for any further help
Unfortunately, the Salesforce accounts once created can't be deleted, but you can deactivate it. If you want to create a new account with the same username first change existing account username and use this username for a new account.
Note: You can't deactivate the username of the system administrator. If you want to deactivate system administrator, please email us at trailhead@salesforce.com and we can assist with account deactivation.
Hope this helps you!
Please feel free to reach us for any further help
Regards,
Jyothsna