When federal student loan borrowers take a breath from celebrating the cancelation of some or all of their federal student loans, millions of them could be in for a nasty surprise: While President Biden’s sweeping student debt relief won’t be subject to federal income tax, in seven states borrowers may have to pay state income tax on all those canceled loans. Before 2021, student debt cancelation was generally considered a form of income, and therefore taxable both at the federal and usually state level. But in March of 2021, the American Rescue Plan changed that, at least temporarily: Until the end of 2025, Congress said, the U.S. government will not…