My mother has been having a lot of health problems this year and has been in the hospital twice (currently admitted now). She has not filed her taxes and I don't think she will be able to do so before the deadline. I live in a different state than her (we are military) and she is elderly with no other help. How can I file an extension on her behalf when I do not know how to estimate her liability? Thank You!!

Aslong as your elderly mother cannot file her return by the due date of her return, Apr 15n2013, then you can request an extension of time to file for her. However, an extension of time to file is not an extension of time to pay. Your mother will owe interest on any past-due tax and she may be subject to a late-payment penalty if timely payment is not made (aslongas she owes tax to the IRS). To receive an automatic 6-month extension of time to file her return, you can file Form 4868 by the due date of her return, usually Apr 15 2014.You can efile form 4868;
http://www.irs.gov/pub/irs-pdf/f4868.pdf