Viewers in Angus, Tayside, Perthshire and Fife are affected by the change.
It means more than 200,000 households will have to retune their TVs and set-top boxes as the latest stage of the digital switchover gets under way.
Around 75,000 viewers will be able to watch Freeview for the frst time as a result of the move.
Paul Hughes, Digital UK's national manager for Scotland, says: "This is by far the largest switchover Scotland has seen, affecting more than 200,000 households and giving many people Freeview for the first time."
Anyone requiring help with the switchover should contact Digital UK.