I agree, you definitely need to get advice on your particular situation to ensure you are meeting your tax obligations in both countries. The fact that you are paying some tax in both countries will not be an argument if either country determine that you have underpaid your taxes in that country. For example, based on 400 days out of Ireland in 2008 and 2009 it is possible that you could be tax resident in Ireland throughout the period and taxable on your worldwide income i.e. including the income from Australia. The provisions of the Double Taxation Agreement between the 2 countries would have to be looked at to dteremine which country has taxing rights, whether credits are avilable etc. It would be worth getting the position clarified. If the Irish or Australian Revenue authorities look into it and take the position that you have underpaid tax, interest and other penalties could apply and the argument that you paid tax in the other country won't interest them.