In order to distribute Apple iOS applications privately within your organization, you will need to enroll in the Apple Enterprise Developer program. As of mid-2014, Apple charges a $299 yearly fee to be enrolled in this program.
The Apple Enterprise Developer program requires a DUNS (Data Universal Numbering System) number to enroll. Apple typically approves Enterprise Developer applications within 3-5 business days. We strongly recommend if you would like to distribute you application privately, you being this process as early as possible.
Apple requires organizations to agree to their terms and conditions. These conditions are primarily in place to ensure that companies will not use their Enterprise account to distribute applications outside of their organization. Apple requires the person approving the enterprise enrollment has the legal authority to agree to these terms.
More information regarding the Apple Enterprise Development program can be found at: