There is no need to delete the account of an Employee who has finished cooperation – just block his account (blocked accounts are not included in the limit of Employee accounts).
However, if you want to delete your account completely, you can delete it from the Organization.
Remember that deleting an Employee account is associated with the irreversible loss of all data (including requests) associated with this account.
By blocking the account, you will be able to view the employee’s full history.