Temporary duty assignment
A temporary duty assignment (TDA), also known as "temporary duty travel" (TDT), "temporary additional duty" (TAD) in the Navy and Marine Corps (or TDI for "temporary duty under instruction", referring to training assignments), or "temporary duty (TDY) in the Army and Air Force, refers to a United States Armed Forces or civilian United States government employee travel or other assignment at a location other than the employee's permanent duty station. This type of secondment is usually of relatively short duration, typically from two days to 179 days in length. Not all agencies use this designation. Some government agencies including the Defense Department mandate they be less than six months in duration. Those agencies that do not mandate a six-month limit consider longer durations to be a Permanent Change of Station (PCS).
Temporary duty assignments usually come with per diem pay, covering lodging, meals, and incidental expenses. Many employees value the per diem aspect of a TDA, since that money is guaranteed, even if they spend less than their allotted daily value. However, some agencies handle the lodging per diem separately from the meals and incidentals, and employees may not make money by staying at cheaper accommodations, or putting more than one person in a room.
Typically, an employee may request a cash advance of 60–80% of the total value of the meals and incidental expenses before the TDA per diem takes place, in order to prevent the employee from having to use his or her own money, or putting money on a personal credit card. Government travel cards are also typically available, though these sometimes carry restrictions on the types of goods or services that can be purchased with them.
Some locations have furnished apartments for long-term stay. These apartments have fully equipped kitchens so TDA recipients have the option to cook rather than always eat out, and some may have free washing machines and clothes dryers. Some government agencies consider any assignment over 45 days as an extended TDA, which allows the employee to be reimbursed for part of the expenses before the end of the assignment.
Examples of TDY assignments in the United States Army include most branches' time at Basic Officer Leaders Course or Gold Bar Recruiter duty after commissioning. In the United States Air Force, temporary duty can be commonly approved by commanders for service at Civil Air Patrol basic encampments or other activities because it serves the organizational mission of recruitment and public affairs. 
- Army Regulation 614–11: Temporary Duty (TDY) Archived 2009-04-18 at the Wayback Machine.
- GSA Per Diem FAQ Archived 2009-05-09 at the Wayback Machine.
- Extended TDY - Details Archived 2009-07-30 at the Wayback Machine., NSSC Customer Service, NSSC Customer Satisfaction & Communications Office
- "AIR FORCE INSTRUCTION 10-2701" (PDF).