There are legal fees involved for a Top-Up. It can work out really expensive if you contact your Solicitor and ask them to look after it for you from Day 1. They open up a whole file and get in to correspondence with the Mortgage provider. Ask your Bank what the position is fee wise. I know IIB have a nominal charge of just under €80 legal fees if they just send the papers directly to your noimanted Solicitor and you just go in to sign, nothing else. It's well worth shopping around on that score.