There will be a guaranteed five the following season as the Intertoto Cup will be replaced with an additional qualifying round in the UEFA Cup.
The team that finishes fourth in the Clydesdale Bank Premier League are likely to take that extra place, but their participation could be at the expense of some of their summer holidays.
SPL secretary Iain Blair said: "The UEFA Cup will start in June and participation is mandatory, whereas the Intertoto had previously been voluntary.
"If a team don't want to start their season in June or early July, they no longer have a choice."
Scotland will retain its two Champions League slots and Blair revealed that the Scottish Cup winners will continue to enter the UEFA Cup in the round before the group stage.
The SPL's third-placed team will begin their campaign one level earlier, in the third qualifying round, while the fourth-placed team will start in early July in the second qualifying round.
The Intertoto Cup has not proved popular in Scotland with only Partick Thistle and Hibs, on two previous occasions, entering since its inception in 1995.
Hibs would be the first Scottish team to gain success in the tournament if they are triumphant in two rounds this summer, the first against Swedish side Elfsborg or HB Torshavn from the Faroe Islands.
Meanwhile, the SPL are yet to hear from UEFA over their request that the Scottish Cup runners-up do not qualify in future.
Queen of the South are the third First Division side in three years to represent Scotland in the UEFA Cup after following Gretna and Dunfermline as cup final losers.