Playoffs go to an automatic overtime that starts once turn 16 is finished, the overtime is 4 turns, if the score is still tied at the end of turn 20, it goes 4 more turns. There is no break in play at the end of turn 16 in a tie game, game just keeps going. That is how the game handles it. So remember that when you're in a playoff game.
Final note, the 4 turns all happen, so if you score on turn 17, the opponent will have till turn 20 to tie the game.