I have not filed my taxes for 2005 and it looks like from my calculations I will owe money. I just filed my taxes for 2006 and 2007 and I will be getting a refund. My taxes were a little more complicated for me in 05 because I took money out of my 401k untaxed to by my first home so that increased my taxable income. I also had a home office for my job in 05. Any tips on deductions, how to file, ideas on penalties or the correct way to file would be most appreciated. Will what I owe be deducted from my 06 and 07 refund or should I send a check for 05? Thank you!

You must complete your 2005 tax return and if you owe any tax, must pay it with interest and penalty.
IRS will not deduct any amount for 2005 taxes unless you have already received a tax due notice from IRS.
Tip. Complete your 2005 tax return and then post your question based on the figures. The sooner you file, the better it is.

I agree with MukatA.

Further, the IRS will put a HOLD on your 2006 and 2007 refunds until you file your 2005 tax return, so you need to file it ASAP.

I really don't know if and why IRS will put to hold your 2006 and 2007 refunds.