The Pokémon Company has announced the details for the I Choose 'Chu! (ピカチュウ対戦チュウ！) competition for Pokémon Sword and Pokémon Shield. Our 8th Generation Online Competitions page has been updated with these details.

I Choose 'Chu! (ピカチュウ対戦チュウ！)

Information
Region: International Registration Period: July 28th, 2022 until August 11th, 2022, at 4:59 p.m. PDT Tournament Period: August 12th, 2022, at 5:00 p.m. to August 14th, 2022, at 4:59 p.m. PDT, Ranking Results Announcement: August 2022 Compatible Games: Pokémon Sword and Pokémon Shield Eligible Pokémon: Only Pichu, Pikachu, and Raichu can participate in this single battle! Battle Type: Single Battles Entry Gift: Qualifying players who participate in at least one battle during the event will receive 50 BP whether they win or lose.
Only Pichu, Pikachu, and Raichu can participate in this single battle!

Register to Battle in the I Choose ’Chu! Online Competition

Show off your shocking skills with Pichu, Pikachu, and Raichu or Alolan Raichu in the Pokémon Sword and Pokémon Shield games.

Get charged up to face off against Pokémon Trainers from around the world in Pokémon Sword and Pokémon Shield's upcoming I Choose ’Chu! Online Competition. You can register now to take part in these electrifying Single Battles—just remember that your team can only consist of Pichu, Pikachu, and either Raichu or Alolan Raichu! Qualifying players who participate in at least one battle during the event will receive 50 BP whether they win or lose. You can register from now until August 11, 2022, at 4:59 p.m. PDT.

To register for the competition, follow these steps:

1. Launch your Pokémon Sword or Pokémon Shield
2. Open the X menu.
3. Select VS.
4. Select Battle Stadium.
5. Select Online Competitions.
6. Select Search Official Competitions.

The competition takes place from August 11, 2022, at 5:00 p.m. to August 14, 2022, at 4:59 p.m. PDT, so don’t forget to return during that time to play your matches. To receive your participation gift after the competition is over, follow these steps:

1. Launch your Pokémon Sword or Pokémon Shield
2. Open the X menu.
3. Select Mystery Gift.
4. Select Get a Mystery Gift.
5. Select Get Battle Stadium Rewards.

Good luck, Trainers—and prepare for sparks to fly in the I Choose ’Chu! Online Competition!

Sources: https://www.pokemon.com/us/pokemon-news/register-to-battle-in-the-i-choose-chu-online-competition/ and https://twitter.com/Pokemon_cojp/status/1552519249075359744