In a large mixing bowl, beat the softened cream cheese and butter together using an electric mixer on medium speed until smooth and creamy, about 2-3 minutes.
Gradually add the sifted powdered sugar, about 1 cup at a time, beating on low speed after each addition until fully incorporated.
Once all the powdered sugar is added, increase the mixer speed to medium-high and beat the frosting until light and fluffy, about 2 minutes.
Add the vanilla extract and salt, then beat on medium speed for another 30 seconds to combine.
Scrape down the sides of the bowl with a spatula and give the frosting one final mix to ensure even texture.
Use immediately to frost carrot cake or cover and refrigerate until ready to use. Before frosting, bring to room temperature and stir gently.