To be announced (TBA), to be confirmed (TBC), and to be determined or decided or declared (TBD) are placeholder terms used very broadly in event planning to indicate that although something is scheduled or expected to happen, a particular aspect of that remains to be arranged or confirmed.
These phrases are similar, but may be used for different degrees of indeterminacy:
Other similar phrases sometimes used to convey the same meaning, and using the same abbreviations, include "to be ascertained", "to be arranged", "to be adjudicated", "to be done", "to be decided", and "to be declared".
These various placeholder terms are often used to indicate to the public that a vacant position in a lineup of speakers, musicians, or other performers remains to be filled. The terms also frequently indicate that a creative work, such as an album or film, is forthcoming but that the date of release is not yet known. If the forthcoming project is not yet named, these placeholders may be used to indicate that the name has not yet been selected, although the project may also be designated as "untitled" pending that determination. The terms are also used in sports schedules, particularly where one team has locked in a position in a playoff schedule, but its opponent cannot yet be determined because several teams may qualify for the spot depending on their remaining wins or losses for the season, or because other teams have not yet competed in playoff games that will determine who will face the locked-in team. In government and business, the terms may be used to indicate that a vacant organizational position is expected to be filled, or conversely that a particular individual will be employed in an as-yet-uncreated position.
"TBA" (meaning "to be announced") is also used to describe a specific type of simple mortgage investment, the forward mortgage-backed security. This is used to indicate that the investor is acquiring some portion of a pending pool of as-yet unspecified mortgages, which will be specified at a given delivery date. This usage has existed at least since the 1980s.