No, you don't get a deduction. The money you put into the custodial account is a gift from you to your grandchild. It is not deductible by you, and it is not taxable income to the grandchild.
If the gift was more than $19,000 you must file a gift tax return, Form 709. You will not have to pay any gift tax unless the total of all gifts that you have given in your lifetime is over $13.99 million, but you have to file the return. A gift tax return is separate from your income tax return. You cannot file a gift tax return with TurboTax.
The grandchild who received the gift does not have to do anything, no matter how large the gift was.
