I was told that 709 is not supported by turbo tax. We already filed our 2015 tax return online through Turbo Tax. We are filing 709 for exceeding the 529 limit in 2015. We won't have any gift taxes. So our tax return amount wont change. Can i just turn in the 709 form alone via USPS? Or do i need to send the rest of the tax forms as well as amended tax return?