The official Pokémon website has announced that the fourth season of Pokémon Sword and Pokémon Shield Ranked Battles has begun and will run throughout March 2020.

Battle with More Gigantamax Pokémon in Ranked Battles March Season

Compete now in the Ranked Battles March Season of Pokémon Sword and Pokémon Shield!

The fourth season of Pokémon Sword and Pokémon Shield Ranked Battles has begun and will run throughout March 2020. Test your Trainer skills in head-to-head battles with players around the world, move up the leaderboards, and earn in-game rewards.

Even more Gigantamax Pokémon are eligible in the March Season. Gigantamax versions of Charizard, Butterfree, Pikachu, Meowth, Kingler, Lapras, Eevee, Snorlax, Corviknight, Orbeetle, Drednaw, Coalossal, Flapple, Appletun, Sandaconda, Toxtricity, Centiskorch, Hatterene, Grimmsnarl, and Alcremie may be used.

You'll be matched up with other players of similar rank to ensure even competition. When the season concludes, the higher the tier you finish in, the greater your in-game rewards. You'll be able to earn Battle Points, mints, Ability Capsules, and Bottle Caps.

To start a Ranked Battle, select VS in the X menu, select Battle Stadium, and then select Ranked Battles. You can press the Y Button to see an overview of Ranked Battles before you begin your match.

Source: https://www.pokemon.com/us/pokemon-news/battle-with-more-gigantamax-pokemon-in-ranked-battles-march-season/