Do you mean that you e-filed already with a mistake? Or do you mean you prepared your tax return and made a mistake you need to fix before you e-file?
What expenses are you referring to that you entered as withholding? Are you self-employed? Did you enter business expenses? Did you prepare a Schedule C?
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**