You cannot report your son's sale of stock on your tax return. Because of the stock sale, he does not meet the requirements for you to report his income on your return. One of the requirements is that "Your child had income only from interest and dividends (including capital gain distributions and Alaska Permanent Fund dividends)." Capital gain from a sale of stock is not a capital gain distribution. A capital gain distribution is a type of dividend paid by mutual funds and reported on Form 1099-DIV. The gain from the sale of stock does not fit this requirement.
Your son has to file his own tax return and report all his income on his own return, including the stock sale.
You cannot report your son's sale of stock on your tax return. Because of the stock sale, he does not meet the requirements for you to report his income on your return. One of the requirements is that "Your child had income only from interest and dividends (including capital gain distributions and Alaska Permanent Fund dividends)." Capital gain from a sale of stock is not a capital gain distribution. A capital gain distribution is a type of dividend paid by mutual funds and reported on Form 1099-DIV. The gain from the sale of stock does not fit this requirement.
Your son has to file his own tax return and report all his income on his own return, including the stock sale.