Other transactions Authority (OTA) is the term commonly used to refer to the 10 U.S.C. 2371 (Prototyping) / 10 U.S.C. 2373 (Research) authority to enter into transactions other than contracts, grants or cooperative agreements. The Department currently has temporary authority to award “Other Transactions” (OT) in certain circumstances for prototype projects that are directly relevant to weapons or weapon systems proposed to be acquired or developed by the Department. OT may be used for basic, applied, advanced research and prototype projects when it has been determined that it is in the Government’s best interest to enter into an agreement that is not a contract, grant, or cooperative agreement (per 10 U.S.C. 2371 and Section 845 of the National Defense Authorization Act (NDAA)). OTs are not covered by the FAR. OTA are a highly flexible business tool, use of which requires application of astute business acumen to ensure smarter, more efficient acquisition of prototype systems for the DoD. OTs require a minimum of at least one nontraditional Defense Contractor participating to a significant extent in the prototype project or a cost sharing arrangement requiring that at least one-third of the cost of the OTA come from non-Federal sources. 
Guide: Other Transactional Authority (OTA) Guide – 17 Jan 2017 (Prototyping)
In accordance with statute, this authority may be used only when: 
- There is at least one nontraditional defense contractor participating to a significant extent in the prototype project.
- All significant participants in the transaction other than the Federal Government are small businesses or nontraditional defense contractors.
- At least one third of the total cost of the prototype project is to be paid out of funds provided by parties to the transaction other than the Federal Government.
- The senior procurement executive for the agency determines in writing that exceptional circumstances justify the use of a transaction that provides for innovative business arrangements or structures that would not be feasible or appropriate under a contract, or would provide an opportunity to expand the defense supply base in a manner that would not be practical or feasible under a contract.
AcqLinks and References:
-  Other Transactions Guide for Prototype Projects – Jan 01
- Other Transactional Authority (OTA) Guide – 17 Jan 2017
- Other Transactional Authority (OTA) Guide – August 2002
- Article: Another Option in a Tightening Budget: A Primer on DoD “Other Transactions” Agreements by Cassidy, Plitsch and Barclay