Switch the Question (or Flip as it was known in the United Kingdom) is a lifeline in the Who Wants to Be a Millionaire? game. When a contestant uses this lifeline, the computer will replace the current question with another one of the same monetary value. However, any lifelines used on the original question are not reinstated and the contestant could not return to the original question, as the computer will reveal the correct answer to the old question before replacing it.
The U.S. version introduced the Switch the Question lifeline at the beginning of its third syndicated season. However, contestants were not given this lifeline until they had successfully answered the tenth question, the second milestone level, so they could only use this lifeline in the top-tier questions. Most notably, once a contestant decided to use the Switch the Question lifeline, its symbol (a 'Q') would appear between the four answers, and would remain there until a contestant decided to walk away or answer the replacement question. It was discontinued after introducing the clock format at the start of the seventh syndicated season, in favour of Ask the Expert.
The UK version originally featured this lifeline during some select special shows, namely the Live 300th show, the 2002 Christmas specials and the April 2003 celebrity specials. On these shows, a contestant could flip any question they wanted at any moment (they did not need to earn it) but, unique to any lifeline on the series, in order to use a Flip, they had to trade it for one of their remaining lifelines, and could potentially use it more than once, even on a flipped question (provided that they had enough lifelines left). Any lifelines that were traded off in this fashion would appear on the money tree menu and the available lifelines box with the Flip logo (a 'Q' symbol).
The Flip lifeline was reintroduced and permanently integrated into the UK show at the beginning of Series 27 with the show's move to the clock format, and was kept until the program finished in 2014. Unlike its original version, which required a contestant to give up one of their remaining lifeline, this Flip was similar to its American counterpart: it was a separate lifeline and a contestant could only use it once they successfully pass the second milestone level (the seventh question). This also meant that the contestant did not have to face the clock when deciding whether to use this lifeline or not.