Uniform Gift to Minors Act Tax Form

We received dividends and sold stock from my son's UGMA account and entered these as dividends and capital gains on his taxes. However, since these are from his UGMA account, the first $1,050 should be untaxed, and the next $1,050 should be at his tax rate, with the remaining at mine. But I don't see any mention of this in my Turbotax questions as I'm filling this out, which I don't understand. That said, where can I get the information to ensure this adjustment is taken into account?

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