A new reason to stick to cohabitation -- if you and your devoted have a giant mortgage. iStockphoto By Sandra Block, Senior Editor From Kiplinger's Personal Finance, April 2017 Getting married may make your mom happy, but if you are a high-income couple, there’s a good chance your taxes will go up. That’s because your combined income could force you to pay a higher federal tax bill than you would have owed had you stayed single.See Also: The Most-Overlooked Tax Deductions Now there may be another reason to break your mother’s heart. Thanks to a change in IRS rules last year, an unmarried couple can deduct twice as much of their mortgage- and home-equity-debt interest. After losing a court case, the IRS agreed that the limits on deductions for mortgage interest—$1 million of mortgage debt plus $100,000 in home-equity financing—apply on a per-taxpayer basis, not a per-residence basis. A married couple is considered one taxpayer; an unmarried couple, two. That means an unmarried couple could deduct interest on a combined $2.2 million of mortgage debt.