Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

Deducting last years (undocumented) side business loss
You should speak to a good tax adviser. The less documentation you have the more problems IRS are going to cause you. Generally you can deduct business losses (in the year they occurred, which is 2011), but you have to show that that was a valid business, not just a way to reduce your tax bill with personal expenses. Thus lack of documentation reduces your ability to prove that you're entitled to the deduction. The burden of proof is generally on you. You can not deduct it from 2012 taxes, but you can still amend 2011. Keep in mind though that amended returns have higher chance of audit, and a significant business loss on a business that only existed that year is a major red flag which will raise the probability of an audit to very high percentage. Theoretically, if the business was real and just failed - you can definitely deduct this. But practically, lack of documentation may cause too big a problem, and a tax adviser might suggest you giving it up if he doesn't think you have a real chance to convince the IRS. Definitely don't do that without a professional advice. It is worth fighting for, its quite a loss, but don't do it on your own as you will definitely lose.