The British Horseracing Authority has announced that all races at next year's Cheltenham Festival will declare at the 48-hour stage.
Previously, only the non-novice Grade Ones declared two days in advance, with the other races sticking to the usual National Hunt 24-hour stage.
However, in a radical move from the BHA, who has been supported by Cheltenham and Jockey Club Racecourses, the switch has been made in response to feedback from various sections of the racing industry.
BHA chief operating officer Richard Wayman said: "We have taken on board feedback from racing fans, the betting public and the media, and we're pleased to introduce 48-hour declarations for all races at the Festival, which we believe will have a positive impact on the promotion of the event and be welcomed by the sport's various customer groups.
"We appreciate that, in some circumstances, this could create an extra challenge for trainers but we want to ensure that the sport is in a position where it can make the very most of what are such an important four days in the British racing calendar."
With the exception of the non-novice Grade Ones, no horse will be able to declare for more than one race - unless it has been eliminated from another contest or declared as a reserve.
All the handicaps will have two reserve slots, the deadline for which will be 1pm the day before the race.