I retired from the military last year in August. I started working for a civilian company around that time. I am now a civilian contractor in Afghanistan. I will be home soon but will miss the deadline by a few days or weeks. I have the extension paperwork ( form 4868). Looks simple but it asks for me to "estimate my tax liability for 2011" I tried to figure this out. All my paperwork is back home and my wife is overseas so I don't have access to everything. I have access to my W2 for the military and my current job. Can I estimate this with these 2 documents? I know it is an estimate but on page 3 it says "If we find your estimate not reasonable, then the extension will be null and void? I have never had to pay federal taxes in the past but this is my first tax year as a civilian. That just reminded me...... do I have to file for and extension for Hawaii state tax? Thought this would be simpler. Thanks in advance.