I work for an MEP Consulting firm doing mechanical HVAC designs for commercial construction. As such, I use AutoCAD extensively. Recently AutoCAD has released an app for the iphone/ipad. I downloaded it on my iphone to see how useful it might be. Recognizing just how useful it is, I purchased an ipad (wanted one anyway). It will be extremely valuable when I'm out in the field doing survey work. Trying to make notes on a 30x42 set of drawings on a windy roof top is a major pain. I have also loaded several other apps that allow me to calculate building loads, calculate piping sizes, etc. My question is, am I allowed to write the cost of the ipad off on my taxes? Work is certainly not the only use for it. After two weeks, the ratio of work use vs non-work use is about 35/65 but I can easily see that moving to 50/50 and the potential to be at 75/25 semi-frequently. I don't want to raise any "red flags" with the IRS but it would be nice if I could write it off.