Thanks for response huskerdu. No we're not getting any mortgage interest relief for our current PPR - should we be?
Yes, you should, but on a non-FTB basis. The allowances are much lower.
I hate to say it, but you could have a liability there as you've been receiving TRS on your non-PPR based on FTB rates and the non-FTB rates you might be due back on your new PPS could be lower.
I have seen people ignore tax issues in the past and they've come back to bite them so I would suggest you try to regularise your affairs but that is your decision at the end of the day.
There is lots of information on de-registering your non-PPR for TRS and re-registering your new PPR on the Revenue website.
I believe the de-registration is done in paper format, the registration of your new mortgage can be done on-line.
And
Just in case you're not familiar with it, your rental income is also subject to income tax. Only part of the interest on the qualifying mortgage can be deducted from the income, the principal repayments can't. Therefore even if there is a shortfall on the monthly payments you can have an income tax liability.
If this concerns you, I'm sure people on the forum can provide advice on how to register for income tax and so on.