Once you have verified your Identity with the IRS, you need to enter a PIN or Signature PIN to sign your 2014 tax return. You can create this 5 number signature PIN on your own. Detailed instructions on how to enter your Identity PIN and/or AGI on efile.com.
Fats or oils (also generally called fats) are added to foods, like crackers, cookies, and cakes, to improve the taste and feel (texture) of foods. Foods become rancid when there is a chemical change to the fats in the food. There are three types of rancidity: hydrolytic, oxidative, and ketonic.
Fat can go rancid, even while frozen (though it does take much longer, I suspect this is part of what @ElendilTheTall was referring to as properly bad.) The higher the fat content the faster it can go bad. If after thawing you are not confident of its safety then yes, throw it out. A fresh pound of ground beef is much less expensive than a trip to the ER for food poisoning.