Reapplying for Tax Relief after Mortgage Top-up?

Do I need to reapply for mortgage interest relief after topping up my mortgage?

What is the top-up amount being used for? It not to purchase/renovate your PPR then it does not qualify for mortgage interest relief. If it is being used for such purposes and your lender does not grant additional relief automatically then you should contact Revenue to apprise them of your change in circumstances. I don't think that you need to or should file a new claim for mortgage interest relief though as that could confuse the system. Just write to Revenue outlining the situation.

Thanks Clubman. The top-up was used to build an extension on the property. I will send revenue a letter today.

I'm thought you could apply for it on the revenue website?

You can do an initial application online. Not sure about claiming tax relief on a top-up though.