I will be coming off a fixed rate this month and my mortgage repayments are going to go up. Do I have to reapply for mortgage interest relief now that my mortgage repayments are higher, or will this automatically be adjusted accordingly?
It will be adjusted accordingly! Just insure that you are put on the best rate when you come off it. I know with AIB a few years ago they sent out a list of rates, which did not include their tracker options.
You definitely don't need to reapply. You may or may not need to flag the change with Revenue. Chances are that you will not and it will adjust automatically. Make sure to keep tabs on your ongoing statements to check.