old or young, if youre not married and have no child, youre Single.

This is a message board for tax professionals, this question is super basic and anyone that is preparing a return in exchange for compensation should be able to answer. 

If in fact you ARE tax professional, please, at the very least, download a copy of IRS Pub 17.  This is covered in Chapter 1.

If youre not a tax professional, please direct any more questions to the TurboTax message boards.

 TurboTax Help site for DIY support, they may be able to help you.