There are several existing threads on married taxation which contain useful information and links that most likely answer your questions. The short answer is that you will most likely be better off (and at least no worse off) if you opt for joint/aggregated married taxation rather than individual assessment or assessment as two single people. Normally you are taxed as two single people in the year of marriage, you claim back any overpayments of tax at the end of the year and then you go onto your choice of married taxation (e.g. joint/aggregated) in the following tax year. Revenue have a FAQ and clear information about this on their website.