The Simple Symphony (シンプルシンフォニー) online competition for Pokémon Ultra Sun and Ultra Moon has been announced on the Pokémon Global Link website. Full details are listed below and on our 7th Generation Online Competitions page which will be updated as new tournaments are announced.

Simple Symphony (シンプルシンフォニー)

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Information
Region: International
Registration Period: Tuesday, January 15th, 2019 (00:00 UTC) through Thursday, January 24th, 2019 (23:59 UTC)
Tournament Period: Friday, January 25th, 2019 (00:00 UTC) through Sunday, January 27th, 2019 (23:59 UTC)
Ranking Results Announcement: February 2019
Compatible Games: Pokémon Ultra Sun and Pokémon Ultra Moon
Battle Type: Single Battle
Banned Pokémon: Eligible Pokémon are limited to Pokémon of a single type, excluding Legendary and Mythical Pokémon. No two Pokémon on your team may have the same National Pokédex number.
Entry Gift: All qualified participants will receive 50 Battle Points.
Description
In the Simple Symphony Online Competition, Trainers create a team using Pokémon with only one type, excluding Legendary and Mythical Pokémon.

The competition features Single Battles with teams of three to six Pokémon, of which three will compete in each match. Pokémon brought in via Poké Transporter will be permitted in battle. All Pokémon will be set to Lv. 50 for the duration of the battles. Z-Moves are permitted, but Mega Stones may not be used. Items are allowed, but Trainers may not have duplicate items in their Battle Team. There will be a 10-minute player clock, with 45-second turns.
Competition Rules
• Items are allowed, but Trainers may not have duplicate items in their Battle Team.
• Mega Stones are not permitted.
• All Pokémon in this competition will automatically become Lv. 50 for the duration of each match.
• Three of the Pokémon you register to your Battle Team will be chosen to battle in each match.
• A 10-minute time limit for each player will automatically be enforced in-game, beginning at the start of each battle. When a player’s time limit expires, that player will lose the game.
• At the beginning of each battle, players have 90 seconds to select three Pokémon to battle with.
• At the beginning of each turn, players have 45 seconds to select a move or change the Pokémon in battle. If a player’s selections have not been made by the end of this period, the game will automatically make selections for the player.
• Players may battle up to 15 times per day of the competition. Any unplayed games will carry over to the following day. A new day begins at 00:00 UTC.

Source: https://3ds.pokemon-gl.com/information/07c197b7-237c-4d15-b2e0-d5d8fcda4a0b