When you get a variable mortgage from TD Bank, the interest rate will be expressed as the TD Bank prime rate, plus or minus a certain percentage point. For example, if the TD Bank prime rate is 3.00%, and your mortgage rate is prime minus 0.50%, your mortgage rate would be 2.50%. Open Variable Interest Rate Mortgage. This five year mortgage option gives you fixed payments and the ability to pay off your mortgage faster. You get the flexibility to increase your payments to any amount, anytime.Plus, you can pay off all or part of your mortgage without paying prepayment charges (an administration fee applies in year one and two only). With a variable rate mortgage, the interest rate can fluctuate along with any changes in our TD Mortgage Prime Rate. Your principal and interest payment will stay the same for the term, but if the TD Mortgage Prime Rate goes down, more of your payment will go towards the principal.