Does a US citizen living in Canada have to file a U S personal income tax return?

Yes you have to file - but that does NOT mean you will have to pay. There are many options for exempting much of your income when living out of the US for more than 12 mos. Plus special rules for Canada....and credits available. Your biggest issue may well be that you'll likely owe Canadian tax!

United States citizens living abroad are required to file annual U.S. income tax returns and report their worldwide income if they meet the minimum income filing requirements for their filing status and age. You must contact the Canadian Government to determine whether you must file a Canadian tax return and pay Canadian taxes. For the United States income tax return, you will have several options available to you regarding claiming a foreign tax credit or excluding some or all of your foreign earned income. References:

• Publication 54, Tax Guide for U.S. Citizens and Resident Aliens Abroad
• Publication 514, Foreign Tax Credit for Individuals
• Publication 597, Information on the United States-Canada Income Tax Treaty