The basic Medicare Part B premium will remain $104.90 per month in 2014. But upper-income seniors still have to pay higher Part B and D premiums if their modified adjusted gross incomes for 2012 exceeded $170,000 for couples or $85,000 for single people. Modified AGI is AGI plus any tax-exempt interest, EE bond interest that’s used for education and excluded foreign earned income. The Part B surcharge for 2014 won’t change, and the Part D add-on will rise slightly. The total surcharges on upper-incomers can be as large as $300.10 a month.