If you are playing a match, for instance on 7 points, then there is a special rule about doubling, the Crawford rule: After the first player has reached 1-away, i.e. 6 points at a 7 point game, doubling is not allowed for one single game. After this game has been played, doubling is allowed again.
I want to explain the reasoning of the rule a little bit: Doubling in Backgammon is always a risk-reward thing. With doubling you get bigger rewards if you win but bigger losses if you don't.
Say, a player takes a 6:0 lead. This player had to constantly evaluate the risk/rewards of doubling while he got his 6:0 lead. Now his opponent gets that for free. After one is 0:6 back, doubling is without risks (it is called an automatic double) because you have to win anyway and if you lose you don't care if you lose a normal game or a doubled game. Thus one usually automatically doubles at the first possible moment.
This could be judged unfair because one player had to work with the cube to get a 6:0 lead and the other gets it for free while trying to nullify the score. Otherwise one cannot forbid the trailing player to double. Thus, as a compromise, the Crawford rule forbids doubling for a single game.