Dependents

Why does Turbotax ask if you can be claimed as dependent by someone else - and if that person will claim you as a dependent? Does this mean that a parent has the choice of whether or not to claim a child as a dependent? If the answer to that question is yes -  that a parent does not need to claim a child as a dependent - then what are the tax consequences for the child? Would this change the deductions that could apply to the child's tax return?