Before it was added to the game, the Headstart had its place.
Its arrival made the highest possible multiplier to increase from 60 to 70. On Mystery Mondays, the use of the +10 Multiplier, the 2X Multiplier, and the Score Booster increases the maximum multiplier to 80.
The Rio 2015 Update increased the highest multiplier possible. With 3 Score Boosters, Mystery Mondays, Special Thursdays and the 2X Multiplier, players can get their multiplier all the way to 104x. However, it is only temporary.
When used, the multiplier will turn blue.
This, the 2X Multiplier and the missions are the only things in the game that can increase the player's multiplier.