Technically, the IRS rule (and you can read this in Chapter 3 of the IRS Pub 17 which is a great resource for individual tax preparation) is that if you are able to be claimed by someone else, you cannot claim yourself. The reality is that the IRS can't tell this and so long as the exemption is only claimed once, there won't be a problem. Your question begs another - who should claim your son? Well, consider that there are benefits to continue claiming him on your tax return besides the $3400 exemption deduction. You can claim valuable education credits (Form 8863) if your income meets requirements, for the tuition of your son's college, whether paid out of pocket or through student loans. Your son could take these credits too - but would not get the full amount of them. Any tax professional that's worth his salt will always look to reducing the total tax burden on the entire family. That means, if possible, getting income taxed at lower rates and deductions reducing income at higher rates. If you make more than $14k a year, you're going to get a better tax benefit than your son would by taking his exemption. In total, even though your son may pay an extra few bucks, the family pays less tax. From our perspective, it's a no-brainer. We let families fight amongst themselves who gets the extra cash :-D. Hope that helps!