I was scammed out of $10,000 by someone claiming to be from the IRS. Can I write this off?

You can claim a theft loss if this scam amounts to a theft under state law. Usually, the taking of money through fraud or misrepresentation constitutes a theft loss. If so, then you must itemize deductions, reduce the loss by $100, and deduct only amounts in excess of 10% of your adjusted gross income.