OK - if you are a single non FTB owner occupier then a maximum of €2,540 (2006) or €3,000 (2007) mortgage interest qualifies for tax relief of 20% at source. This means that your repayments should be reduced by €2,540 @ 20% / 12 = €42.33 p.m. in 2006 or €3,000 @ 20% / 12 = €50 p.m. in 2007. As I say this relief should have been granted at source by the lender and if it wasn't then either they or Revenue may not have up to date details about you, you may need to sort this out and claim for outstanding relief over the past 4 or fewer years.